Here is one trick I learned: I take the digital, put it in a padded waterproof box, and keep it in a pack or box, somewhere that it will stay cold. I keep the batteries in my pocket where they will stay warm.
Since the camera is cold, the lens won't fog up, and since the batteries are warm, there is power. This theory has been tested to about -30 at crescent lake on the kenai pen. There are definitely never winter openings down here on the road system... too many people for that....