Horn and Hyder are both located along the tracks and can be viewed via google maps here:
32.976766, -113.434339
A friend of mine has the Employee Time Table for the RR during that time period that list all the stops. He said he would bring them over early next week. He did say that Hyder had a stop or siding withing the camp. With the amount of equipment that came to the Desert Training Center during the early 40's there had to be some sort of off loading spot for the Military outside of the public facilities.
Dateland, I believe was just a water stop, not an actual depot, but I'll be able to look at the official documents next week and possibly scan them to post here.
He's got a lot of history for the RRs that is very useful, including local history of this area, in talking with him, he said the majority of soldiers that passed through Horn and Hyder would take passes to Phoenix and also, the military pretty much took over Aqua Caliente as a "resort" for the officers..located here:
32.984976, -113.324213
regards,
Jim