I'm in Ottawa too and our daughter will often nap in her stroller at temperatures of -10C or more while we're out for a walk. I probably wouldn't specifically stick her outside for a nap but in general the cold (or indeed sleeping in the cold) is no big deal for kids as long as they're dressed well.

You'll probably find that in most cold places.

Here in Minnesota, the preschool and kindergarten I'm familiar with have the kids play outside at recess at least 2x a day unless the temperature is below 0F (I think; it might be -10F). Considering that the temp here can stay below freezing essentially continuously from mid-December to early March, it makes sense. Otherwise the kids would never get to play outside for months.

We live in the snowy mountain town of Park City, Utah and our kids have a long recess break during school where they play outside no matter how cold and snowy it is. The only time they have to stay inside if if it's warm enough to rain. So there are places in the US where people aren't neurotic about kids being cold. But we're big into winter sports and being outside here.