Airstreams, especially vintage ones are really intended for three-season use. I wouldn't think of full-timing or spending lots of back-country camping in the winter months. A weekend "roughing it" is one thing...using it for home base for an extended period of time in the winter is another.
The biggest concern I would have is two-fold - water & heat. In the vinatge trailers, some of the water lines and the black tank are under the floor and that area is not
heated unless there is a ducted under floor furnace. Your black water system would pretty much be out of service in the mountain winter temperatures. Staying warm is not as big of a problem by itself, as long as you have lots of propane, you can keep toasty warm.
Another concern is condensation...they don't have dual paned glass and aren't insulated well enough to keep if from forming - especially with cooking moisture (and showers if you figure out the water thing).
One of my all-time favorite "winter threads" is by RubySlipper
- if you haven't yet read it, it's a hoot and gives a down to earth perspective from the field!
If you were down here in Denver - no big deal most winters, but in the high-country...it would definately be an adventure
! Not sure if it would be the kind you are looking for though ~
Good luck in whatever you decide to do!