Welcome.
About RR property....
Out of all the different kinds of sites to detect the ones owned by the railroads are some of the most difficult to get permission for.
On tracks that are being used they are afraid of people getting hurt and since 911 they watch them even closer and on ones that aren't being used they usually turn you down...even if you can find someone to ask.
They have their own police force and those guys don't mess around, confiscation of your equipment, heavy fines and even jail time are all possible.
I suppose some old tracks out in the middle of nowhere that haven't been used for decades it might be possible, if you do ask permission the worst they can say is no but they usually have a bunch of garbage metal around them anyway.
Closer to old abandoned depots might be better but like graveyards I won't go near them.
Too many bad things can happen.
If you want to try good luck with that, I prefer nice safe public parks instead and other public sites.