Switchback (1997) was one of a number of movies filmed on the standard gauge Rio Grande system. You can find more information about the movie itself in its entry in IMDB.

Equipment

The locomotives used were not Rio Grande at all, but rather a pair of ex-Southern Pacific SD39s repainted into the Rio Grande scheme (though the orange was significantly off...) These locomotives went on to become ANDX 4027 and 4028, and regularly hauled the Andesite Rock train from Carr, CO, to near Denver via UP's Greeley Sub. In 2001, they were sent east to the Dakota & Iowa Railroad, where 4028 was eventually repainted into that road's yellow and black scheme. To my knowledge, 4027 retains its fake Rio Grande scheme, though badly faded.

The plow/spreader used at the end is actually D&RGW AX-044, repainted for the movie. Today, it's preserved and on display at Hot Sulphur Springs, CO.

Filming Locations

Filming locations were all over the Colorado portion of the standard gauge system, including La Veta Pass, Gore Canyon?, the east end of the Moffat from Denver to the Tunnel