Its never that cold in Oslo. -10C is not that common. Very short periods of -15C maybe. For the most part between -5C to +5C from Nov to Mar/ Apr.
With respect to cameras. Had you been talking about a classic leaf shuttered camera, I would say get it CLA'd, and take out for shorter periods of time only. A modern camera like the Fuji's, no problem. My D300 I'ved used in -20C all day long. The most sensitive part of the camera in the cold is the battery. I've also used my X-E1 in sub zero temps for several hours at a time, it works perfectly.
EDIT: Also take into account acclimatising the gear when going in and out of the cold. The lenses may fog up when going indoors especially.
I live in Minnesota, and it gets far colder than it does in Oslo typically. I haven't had a problem with any of my cameras. Batteries go faster but it's not super-speed or anything. You'll lose 15-20% (my estimate) if you're out for a long period of time.
Lenses fogging up can be an issue, and I'd advise NOT swapping lenses out on a digital body until it's acclimatized to the indoors again, for fear of getting condensation on the sensor. I'm not sure what that would do, but I wouldn't try it out.