On the line over Cumbres up until 1951 there was daily passenger train service in both directions, this alone helped keep the line open. The problem areas were areas prone to drifts, usually cuts and other places where snow could accumulate easily. There were many times when the San Juan got stuck in a drift and had to be rescued all the way up until the end of it's active service. The bridges normally didn't accumulate enough snow to warrant a dozer to cross it, a locomotive would take care of that. I would not want to drive a dozer across Labato or Cascade trestles in dry conditions! Interesting topic and conversation. Remember that OU also had a plow built on the front of it, so it could also be used to plow off a bridge. When the D&RGW first got the OU they would push it in front of the locomotive. I have several pics of a new OU painted black being pushed by 478. I think the D&RGW soon learned the OU could be more effective as a spreader and not a primary plow. I'll post some photos of dozers and snow fighting equipment later.
William
aka drgwk37