I commuted in the Rockies last 3/4 winters... Although my area isn't especially snowy and/or cold.
I used regular 2.25" tires with decent threads, no studs. If you can keep the bike very upright you are fine without them. Can you take a fall? I had about 2-4 a winter and they were usually fun and slow events from heavy snow.
Very cold temperatures held with slipping, so you're in luck there ;)
What type of terrain and surface will you be riding on? Are you on plowed, paved roads? Or will you have to use un-shoveled sidewalks and paths?
If you can use plowed streets without too much danger from cars, I think you're fine with regular tires... If you're going to be a snow plow you might want to get/make some studded tires.