Last three seasons I've been commuting in and out of Oslo all year round, regardless of weather...even during the worst of snow storms. After too many very close encounters, I finally ate it... and got just a tiny bit wiser, and decided only to ride if condtions were good and the forecast promising.
Spiked tires and rough thread can do only so much for you. Even if you can stay up right on flat straights, down hill can be impossible if it is slippery and you have to slow down or come to a full stop... even controlled braking from the slowest of speeds and you will either fall over or not stop until you crash into something - no ABS or rider skill in the world can keep the bike up if there is no grip and gravity is at work. Riding is usually not the biggest problem - stopping is... which you will have to do a lot of in and near towns.
Imagine deep loose snow, with some ruts and ice underneath, in a bend on a slight downhill slope, right before an intersection... you are riding at 20 kmh with your feet down, trying to slow down for an oncoming red light with crossing cars and pedestrians, without falling over. You are thinking that if you are so lucky to be able to navigate the turn, there is no way in hell you will be able to stop at the light - this as gravity wants to take your bike, down, down, down, the slope, like a heavy sled. You find you are so right, it appraoches all so slow, and so far ahead... there is ample time to try anything before reaching the intersection, and you do. In fact, you could probably have made a nice long prayer if you had your calm about you. But, there is nothing you can do... you navigated the bend somehow, but tires are locking up even with ABS, and the only thing keeping your bike upright is your legs, with your feet fimly sliding accross the road... you are no longer sitting, you are standing/sliding on the ground, holding the bike up by the handle bars, slightly askew, but still moving forward... and miraculously you somehow slip through to the other end, among all the pedestrians and passing cars, all missing you by inches in both directions... and everything is ok, and you are utterly stoked "Yeah baby!". Riding in snow can be quite exhilerating!
Then, a hundred meters later, having sped up a bit on a "safe flat stretch" while making a mental note to get some snow chains, a taxi cuts in front of you and slows down just enough for you to have to put on the brakes, and you slam into him... Nothing big, but you come to an understanding with mother earth, not to ride in these conditions again.
There are lots of hills with lots of traffic in the alps, and snow and ice does happen, even without your permission. If the road is dry - no problem. If the road has ice and snow on it, it can still be ok with spiked tires as long as it is relatively flat and straight and you don't have to do much stopping. And if there is no traffic, then it can be super exiting. But snow on black ice on bendy hilly roads with traffic????
a few winters ago I witnessed a French biker in the Norwegian mountains that couldn't make a right turn and slided into the oncoming lane where he was run over and killed. It was nothing he or anyone could have done to avoided the accident except not have ridden at all.
If you are prepared to sit it out until roads are throughly cleared (which could be a very long time), then I'd say go for it... after getting the appropriate tires and snow chains for extra measure. If not, then I would advice against it.
Please don't ask me where to get snow chains as I have no idea.