The SD70ACS's are specifically designed for the extreme conditions found in a desert including, extreme temperatures.
Some of the models special features are - a pulse filtration system, movable plows located on the pilot and the trucks; and a fire display system.
I read that, some of these special 70's are built lighter, to meet specific local regulations, but still have the traction capability, required.
I never gave it too much thought... railroading in the desert, but it must look kind of cool... those big machines, blasting over the sands. Guys over there would have great visual scenes to model, especially the camel crossings.
Rick