Be careful with glasses, watches, jewelry and zipper pulls. Small metal and plastic objects can get cold enough to cause frostbite. Carry an extra clothes layer, about 20 degrees worth. Windshells, an insulated jacket, something to keep you warmer if you have to walk for a while. If your feet get cold, run with the bike.
Mushers always have the right of way.
Get fully off the trail early to let them by. Dogsleds can be vey quiet and very fast. They can surprise you from behind or head-on. Even a well prepared bicycle isn't at its best then. Steel gets more brittle at winter temperatures but I haven't seen any steel frames or components break from the cold.