Shot appers to be on the curve passing what is otherwiase known as Lake Lobato.
This was the second day of the 1975 Rotary run. Behind 487 was the Rotary Cook Car, an open gon (?) and 0503. When they dug into the hill, 487 spun to a stall because of ice that formed the rails overnight. Eventually, they cut the trailing cars off and the fans walked ahead of the train while OM and 487 did a continuous series of runbys all the way to the east side of Lobato Trestle.
Finally they decided to call it quits for the day. Everyone piled into the OY and on to the tender and they backed down the hill to the train where everyone unloaded and went back into the cars for the ride home.
The only guy I can 100% identify is Gary Getman riding the rear step of 487's tank as they back down the hill.