I've done winter cycling in Winnipeg, Toronto, Saskatchewan and the Okanagan. In each of those places, people have questioned my sanity but motorists have given me a lot of room on the roads.
In Winnipeg, I used a cheap road bike. I used that bike and a mountain bike in Toronto. Since then I've used mountain bikes for all my winter riding.
The coldest I've ridden in is -35 C in Winnipeg. Yeah, it's cold, but it's not too bad. Below -20 C, it tends to get quite dry. The ice isn't too slippery and the pavement isn't messy for riding. When it's close to the freezing point, winter cycling becomes a challenge. At those temperatures, it's wet, slushy and slippery. And in Toronto, the salt on the roads is mean to steel bike frames and to chains and other components.