Continuity mistake: At the start of the movie the train pulls into town. The loco, tender and 2 stock wagons pass the water tower, but the next shot shows the loco still alongside the water tower.
Continuity mistake: In the final shot as the vintage train pulls away we see the back of the caboose pass by a very large satellite dish.
Answer: It was established that railroad tracks were put through the desert. Probably a shortcut to save time or it was the only area they were allowed to build. Land deals, claim jumping and protected grounds were a big part of where tracks could be laid. It was after the train disaster that the tracks were discontinued.