The 476 didn't get to stay in the Durango roundhouse for long. After bringing in 115 it went out as a helper east as far as Falfa. The 453 that was used as a helper east of Durango previously was used on the Silverton train. That answers my question of not running the helper through to Chama. It would have created an engine shortage at Durango.
Also, a minor detail. J.C. Hall is listed leaving Alamosa west at 3:50 p.m.on the 488 and also running a Cumbres Turn out of Chama at 7:40 p.m. on the 489.