John,
I think what some people forget is that the C&TS is owned by the states of Colorado and New Mexico. It would be hard as hell to tell a taxpayer that even if not a resident of either state, that they cannot take pictures of public property.
The only time I was ever concerned about someone flying near Eureka was when a helicopter closely paced Eureka. It made a LOT of noise, obstructed the view of a lot of people and was like a giant gnat flying with us. It hasn't happened since then and so I have not said anything.
What all photographers should do is simply be considerate of others. If they want to fly their drones to get high shots or whatever, that is fine. But at least keep at a prudent distance so as to not annoy paying passengers for that trip. There is no hard and fast rule that can be laid down. Just use good judgment. After all, we run our equipment so all the public can enjoy it.
I do remember one time on the C&TS when we were bringing Eureka down the Cumbres Pass on a very dark night. All we had was the oil burning headlamp to see our way. As we got down the grade, we came upon a grade crossing where a number of photographers had a bunch of VERY bright lights including car lights shining right in our eyes literally blinding us from seeing anything in our path. All of us in the cab were furious at such unsafe and inconsiderate conduct. A very serious safety issue was created by this type of conduct, all to get a lousy picture. Other times I have seen guys park their car right on the grade crossings, get out leaving their car on the crossing and take pictures of Eureka coming at them....they would not move even though we frantically set up brakes and had the whistle and bell screaming....only to move their car at the last moment. Safety is where I draw the line.
Dan Markoff