It really looks like the Morenci southern, but I cant place the exact location either. At times The Moctezuma Copper Co. Railroad shared motive power with the Morenci Southern including some of the 2-8-0,s but this is clearly not the Moctezuma line. One idea might be to get a geological map as the rock outcropping is that weird sedimentary conglomarate found south of the San Francisco River that looks like it is about to crumble, yet is strong enough to tunnel without lining. A geological map will show that rock type and help narrow it down.