I had recently seen a video of a train at Cumbres where the 487 which was the mid train helper was cut out and ran around the train and then coupled onto the front of the 493 which was the road engine. They both pulled the train over the "hump" and the 487 was cut off right before the hiway trestle and then ran light to Chama. I believe this was SOP. I also think I know how eastbound trains were assembled so the raod engine wouldn't have to back an entire train to get everything coupled. I will post this theory later today. Hope this kinda explains it.
William