Please, for any questions about old railroad rights-of-way, ask me.  I spent five years valuing them and non-operating RR properties for Southern Pacific, now absorbed by Union Pacific.  If fact, it was my office that valued the line from Red Rock (on I-10) to SASCO (Silverbell) for abandonment.  The tracks were then long gone, but the right-of-way still existed.   ...all gone now, without a trace remaining -  not even any evidence of it on your map, which is strange as it was an important line.

There was also a narrow gage from the mines at the orignial Silverbell camp to the smelter at SASCO.  That road bed can still be seen in the area.

As to the line that went from Benson to south through Bisbee, passing near Tombstone (with lines servicing Tombstone - not on your map) that is abandoned as marked, with much of it sold off and not easily available to make a new line. 

There are also a number of other historically important old lines not on your map, perhaps because it only reflects abandonments since 1950. 

For what it's worth, the costs to make a new right-of-way is very expensive, exceeded only by the costs to re-assemble one previously abandoned.  For this reason, I just can't see any new RR lines going into these areas.  Some levels of on site processing will be required to reduce the amount of material that will have to be transported for further reduction.  That means trucking and/or slurry lines.

VP