Back to the basic question.
Is leaving a camera in a cold car a bad thing?
Aside from the obvious risk of theft. There is no real harm in leaving a camer in a cold car. A point taken that has already been mentioned is about the definet risk of condensation inside the lens when moving the camera to a warmer more humid envirnment. Although bettery life does suffer from cold weather, one good thing about shooting in a cold envinment is NOISE, or in this case, lack thereof. How can this be you say. Simple, the noise is the by product of heat building in the imager. Since the camera is in below standard temperatures the imager doesnt get as hot and therefor produces less noise.
This is also why, generally speaking, CMOS sensors have less noise than CCD imagers. because they use less power, and there for generate less heat. No a tremendous amount of difference mind you, but just enough to tell. Um, did I stray of topic here? :wtf ah well, happy shooting