We used that Boarding facility in June 2015 while we rode the train.
As you described it is a chain link kennel with straw bedding, nothing fancy but more than adequate with fresh water available. What more do you need?
The dogs were safe, protected from the weather, and un-bothered while we rode the train. No body groomed them, bathed them or painted their toenails while we were gone, they just had to stay in a kennel and wait.
As pointed out there is not a lot of choices available in the area. And, what difference does it make if the vet clinic is mobile? the kennels are stationary:).
Nobody is fussier about dogs than my wife and yet we all managed to live through the experience of the Chama Vet Kennels.
Have fun riding, take the bus to Antonito and ride the train back to Chama.
Tinbender