My thoughts as a botanist:
Big ponderosa pines like Juke's Tree will often be well over 100 years old, so it may be as old or even older than the railroad itself. Has anyone ever taken a coring of the tree to count the rings? How far back in the photographic record does the tree appear?
Do the Jicarilla Apaches have any traditions about the tree? They've been in the area the longest so they would presumably know something about its history.
Water supply is critical to big trees, so one thing the tree probably has in its favor is proximity to the Rio Chama. Ponderosa pines tend to have wide-ranging root systems, so it wouldn't surprise me if it's dipping its toes in the river and drinking up.
There are a lot of limbs missing on the track side of the crown, no doubt killed back by locomotive exhaust, but the other half looks pretty good to my eye.
-Philip Marshall