While I don't think we should make them mandatory but, I also don't think we should compare Quebec to Ontario. Freezing rain, ice, slush and rain are very common during the winter season and while all winter tires are not created equal, I'd say most will out perform all seasons in these conditions.
Just because you can drive with all season during these conditions, doesn't mean you should.
I passed so many struggling SUVs/4x4s with all seasons last night, right along with most other cars or vehicles equiped with winter tires.