They might have kept one engine in Durango - just in case. I don't know where the 470's were. They also had 464 in Durango too. The fact that they turned 488 and sent it back to Chama almost immediately makes me think they needed power in Chama asap and there wasn't anything else to send over.
I've seen some Norwood pics of the 480/497 train with the cats dozing ahead. Plowless 480 is on the point creeping up the hill while 497 (with plow) is backwards on the rear to get the train back home that night. It took a few days to reach the OM stuck up there at Coxo.