During the summer months it's great though.
According to wikipedia, average lows in Oslo are about -5. That's pretty warm. Salt still melts snow at those temperatures. Even sunlight will melt snow on pavement at -5. But below around -10/-15 salt stops melting ice, vastly increasing the manpower needed to clear roads/sidewalks. Clearing ice at proper winter temperatures requires mechanical means, hammers, if not propane torches.
Biking was practically impossible (and very dangerous), and sometimes even walking a few blocks was a challenge. That being said, I’d still advocate for places like Edmonton being “15-min” cities, and in-fact it would make it much easier in the winter when transportation is more limited.
It's good to have warm clothes for your extremities, but your core gets surprisingly warm when you bike with any kind of coat on. I often just wear a think goretex jacket till it's in the single digits fahrenheit. I wear winter boots, warm gloves or mittens (depending on how cold it is), and a balaclava or gaiter. Also ski goggles for really cold/windy weather. If you don't start off feeling somewhat cold, you've overdressed.
I tried studded tires, but found they didn't help much. Black ice is rare here compared to layers of snow and slush, which don't give studs much to bite into. For me, three inch tires with an open tread pattern at low pressure -- plus an upright riding position that distributes weight evenly between the wheels -- gives me the most confidence.
Regarding the cold, I'd say windproofing is most important, and expedition-style mittens are well worth the investment. You won't need much insulation (except maybe at the extremities) once you start generating body heat. Multiple top layers, each with their own full length zipper, will let you regulate your temperature without getting off the bike. That's especially helpful if you have long climbs and long descents.
In heavy bike using cultures, people have gear ready to go. Spending a minute to put it on is not really a barrier, an inconvenience. If there is a practice. If your environment supports it, by having plowed routes for bikes, bike parking.
I think we overrate the convenience & comfort factor. Don't knock it till you be tried it. You might like it! There is some real difficulty when your society self selects to only support & assist one mode of transit, doesn't have bike parking readily available, doesn't have safe paths for biking. And trying to embrace biking on your own, learn how to do it comfortably & safely, when few others do, that's hard. But I think the inherent comfort g convenience of cars is somewhat/greatly overrated. The mindset is that biking is inconvenient, but so many who successfully live it will tell you, it's easy & it feels great.
there's also the issue of those with pre-dawn and night commutes, these people are disproportionately lower income and live farther and farther away from gentrified city centers. it is not uncommon to see as much as a 20+ degree drop once the sun goes down and you'd better hope there's no windchill on top of that.