The decision in McCarthy v. 2065943 Ontario Ltd. provides a good summary of the principles applicable to the notice requirement in s. 7 of the Proceedings Against the Crown Act:
18. The legislation in s. 7(1) offers a much more forgiving limitation period with respect to tort claims, employment claims, and statutory claims, but s. 7(3) imposes the 10-day deadline for notice “in respect of any breach of the duties attaching to the ownership, occupation, possession or control of property”. This 10-day notice provision is considered an essential step in a proceeding against the Crown when occupiers’ liability is concerned, and for the most part it must be strictly observed. Failure to comply with the notice provision renders the proceeding a nullity: Zuliani Ltd. v. Windsor (City) (1973), 1973 CanLII 671 (ON SC), 2 O.R. (2d) 598 (H.C.), at para. 6.
19. The purpose of this notice requirement is to “target occupiers’ liability” with a special and strict notice requirement”: Latta v. Ontario (2002), 2002 CanLII 45117 (ON CA), 62 O.R. (3d) 7 (C.A.), at para. 18. Such notice has been held to be driven by a policy that permits the Crown to gather sufficient information either to seek to resolve a claim or prepare a defence to an anticipated action: West v. West, 2013 ONSC 247, at para. 14; cf. Mattick Estate v. Ontario (Ministry of Health), 2001 CanLII 24086 (ON CA),  O.J. No. 21 (C.A.), at para. 15.
20. Strict compliance with the notice provision has been relaxed in certain circumstances. Thus, imperfect notice that takes into account the frailties or limitations of an injured plaintiff may nevertheless be deemed sufficient to put the Crown on notice that a claim could reasonably be anticipated: Latta, at paras. 30-35; Leone v. University of Toronto Outing Club,  O.J. No. 4131 (Sup. Ct.), at paras. 75-76. Moreover, there is no indication in the PACA that the notice must be in writing, written by the hand of the plaintiff, or be in any particular prescribed form, so long as it provides the requisite elements of proper notice: Coulter v. Ontario (Ministry of Natural Resources), 2014 ONSC 1573, at paras. 61-67.
The court also explains why attempting to circumvent the notice requirement by framing an occupier’s liability claim as negligence is fraught:
21. No notice to the MNR was given by anyone within the ten days following the date of the incident in this proceeding, August 10, 2014. Even on a generous interpretation of the PACA, reading a “discoverability” requirement into the determination of the date that constitutes “after the claim arose” for the purposes of a third party claim under 7(3) of the PACA, no notice was provided within 10 days of the date the defendant points to for discovery of the claim, July 11, 2018. Notice to the MNR was not provided until September 14, 2018, more than 60 days after the “discoverability” date.
22. The defendant raises two main arguments against the PACA notice requirement advanced by the MNR. It asserts that its third party claim addresses negligence, and not occupier’s liability, and is not therefore subject to the 10-day limitation. It further submits that no such notice is necessary in the circumstances of this case, and that the MNR has suffered no prejudice from the absence of notice.
23. The defendant argues that its claim involves negligence of MNR servants and employees in the placement, clarity, and maintenance of necessary signage, and is not a claim “in respect of any breach of the duties attaching to the ownership, occupation, possession or control of property.” On such an argument, the claim relates to negligence, and not to occupier’s liability, and is subject to the more lenient notice requirement in 7(1) of the PACA.
24. However, such an argument rings hollow in the circumstances of this case, where all of the defendant’s allegations in its third party claim actually appear to relate to issues of occupiers’ liability, and duties attaching to the ownership of property. Indeed, a claim that is, in substance, “in respect of a breach of duties attaching to the ownership of property” does not escape into the tort claim provision under 5(1)(a) of the PACA, so as to bypass the 10-day notice required for s. 5(1)(c) property-related claims, merely by disguising its true nature under an over-arching assertion of negligence: Daoust-Crochetiere v. Ontario (Minister of Natural Resources), 2014 ONCA 776, at para. 3; Latta, at para. 18. This argument fails.
25. Given the passage of time before the defendant became aware of the signage issue that was raised by the plaintiff only at her discoveries, the defendant submits that the purposes served by strict application of the notice requirement cannot be fostered in any way in relation to this third party claim, which almost necessarily arose much later than ten days after the date of loss. By the time the defendant was served with the plaintiff’s claim, the MNR’s opportunity to investigate was already significantly attenuated. It is submitted that strict application of 7(3) of the PACA to defendants seeking to launch third party claims will result in injustices.
26. The defendant also argues that in this case the MNR suffered no prejudice as a result of the failure by the defendant to provide notice, as Ms. Snarr conducted her own investigation that must have contemplated the possibility of litigation, since the MNR now seeks to wrap her report in “litigation privilege”. The defendant argues that the policy behind the PACA notice has therefore been met, even if the notice requirement has not been.
27. To accede to this argument would require a court to read into the provisions of the PACA an exception that its legislators did not see fit to include. While some areas of plaintiff incapacity have resulted or may result in a forgiving application of the PACA notice requirements in certain circumstances, such as with respect to the form of notice, a flexible approach that would bypass a notice requirement altogether, even in the absence of prejudice to the Crown, reads into the legislation an exception that does not exist. The Ontario Court of Appeal has specifically rejected such an approach: Daoust-Crochetiere, at para. 12.
28. This argument also does not take into account the elements that make up proper notice under the PACA. Adequate notice must contain both sufficient particulars to allow the Crown to identify the source of the potential problem, so that it can investigate, and a complaint in some form, to alert the Crown to the importance of investigation to avert a potential claim or prepare a defence to an impending claim: Latta, at paras. 26-27, 42; Mattick Estate, at paras. 15-18; Conners v. Ontario (Minister of Community Safety and Correctional Services), 2016 ONSC 7238, at paras. 21-22.
29. The Crown had a right under the legislation to be alerted to the defendant’s third party complaint relating to signage long before September 14, 2018, so that it would be encouraged to conduct what investigation it still could in as timely a way as possible. Ms. Snarr’s report, though it may contain significant details of the incident, the names of individuals involved, and injuries sustained, has not been shown to have been directed to the plaintiff’s allegations about improper signage in the Park. This argument must fail.