As this Hamilton ON woman found out after an accident in London, ON, she got billed for calling 911 to have EMS check on her young daughters after another driver hit her family's vehicle.
https://toronto.ctvnews.ca/ontario-w...-911-1.5709157

I'm aware that Burlington ON also will bill non-Burlington residents for any emergency services responses/assistance.

So it might be worthwhile to explore if your existing automotive insurance covers surprise emergency bills or to consider buying extra coverage for out of town visits within Ontario. Don't forget to also examine any auto membership-does it cover such bills?