I don't envy the crews which were subjected to Winter conditions and all types of weather. Their standard issue was a rubber type cape over wool which doesn't compare to today's high tech materials. Those bikes (and riders) must have been tough to withstand the conditions and loads they carried. I wonder if they had chains or special snow tires? Some of the rigs did have a driven sidecar wheel and dual range transmissions ( w/ 2 reverse gears) which would greatly help out in the snow. The Russian built Urals' use somewhat of the same setup on some models.
When there wasn't an actual road it looks like a railroad bed would do. I've been on a few roads that felt kind of like that. These guys look like they are in for a bumpy ride. You'd think it would rattle the bikes apart.
The guy seated in front doesn't appear to be enjoying his ride too much. Probably isn't very warm, looking at the terrain and the gear they are wearing. I don't think the US military used too many sidecar rigs. They used a lot of bikes for messenger purposes, but not for offensive purposes.