The experts have cracked the case. It is actually a Phelps Dodge Industrial Railroad train in Morenci. The center car is former Morenci Southern parlor/coach 102. The car behind is a former Coronado RR open "Frijole Express" car the first one is a rebuilt Frijole car with windows added.
All of it is 3' gauge. There appears to be piece of 36"/20" dual gaug in the foreground.
Pic was taken in the late 20's early 30's before PD shut down in the depression. The Morenci Southern was abandoned by then. The Shannon Arizona RR had built a line from the A&NM (SP) yard in Clifton up to the what became PD's smelter in Morenci. They used a portion of the MS from south of the smelter up through the plant and into Morenci, where the pic was taken. Probably be this time the triple loop track arrangement in the canyon below Morenci had been replaced by switchbacks.