When photographing trains, I have rarely ran into issues. I use a telephoto lens on active tracks and stay out of the right of way. However I was told by an Amtrak employee that it was against the law to photograph trains at 30th street station. I did not argue the point. I had most of my photos anyway. However at Harrisburg I asked permission to go down to the platform early before a Keystone Service train started boarding to photograph GG1 4959 and I was told I could photograph anything I wanted as long as I stayed on the platform.
While it does not operate nearly as frequently as it used to, the Apache Railway in northern AZ will allow you to access the entire property if you sign a waiver and follow their rules. I have not made the trip yet, and need to soon as they still operate an all Alco fleet. The Copper Basin about 2 hours from Phoenix has a similar policy.
