OK guys, Thanks for the scoop. I kinda suspected that with a large fortune in locomotives parked out there, it might be prudent to have full-time security. I remember years ago UP stored locos at Yermo, which was another very dry location.
This part from Trainorders is interesting, assuming it's accurate:
Please note that Union Pacific didn't pay for this project, the Arizona Department of Transportation (ADOT) did. Interstate 10 thru the area isn't up to regular interstate standards and both the March Station Road overpass and the nearby Union Pacific overpass were too narrow and too low to allow high/wide loads to pass thru on the interstate. This required a long detour over narrow state highways with many curves and grades. Instead of replacing the UP overpass, the ADOT and UP agreed to straight line the track thru this area. The original line starts on the north of I-10, crosses the freeway, goes thru the horseshoe, crosses under the freeway and then continues east on the north side of I-10. This new alignment just keeps the tracks on the north side of I-10 all the way. The Marsh Station Road interchange for I-10 was moved a couple miles east and a new, interstate complaint overpass was built.