That's news to me! Admittedly, I haven't been on a highway in Ontario in ~2 years, but I definitely never saw signs like that then (of course, I definitely saw people exceeding the speed limit by 50kph on more than one occasion, and given how quickly my uncle made it to my grandparents' house in Ontario the last time he headed over from Montreal, I suspect he may have too ;).

- Canadian raised in the US, spent a fair amount of time in Canada