No, they are not hauling a locomotive. They will run short trains out of Chama, at least this is what I've read!
In your plan you have the cost of moving passenger cars and a locomotive. No, their is not enough passenger cars in Antonito to make up two trains, the majority of the cars are in Chama. Also, their has to be a way to get the locomotive serviced and a way to dump the ashes. I think this would cost more money than it would help. The short trains out of Chama might be a good idea since it offers people who have little money or little time to ride the train!
My two cents..