Having had a bus in conditions like that on more occasions than I can remember I can say that Bryan points out something important to remember and that is the impact of parking on a layer of snow. To add to his comments, if you do find yourself having to park on top of hard packed snow make absolutely certain the spot does not slope sideways. You may be able to level your bus, but if you find yourself stuck and need to work the bus out of the spot it will slide sideways if it cannot roll forward. If you have plenty of open spaces all around you a sideways slide is no big deal, but if that is not the case you could be in trouble.

As to freezing brakes, unless it was raining or the brakes got wet and then froze after parking it is not likely the brakes will freeze, but if you have moisture in your air system, especially the aux system and the suspension you could have problems because the valving is not likely to work real well.