I suppose I likely gave bad information in my first post. And don't want to do that.
My experience has been very different than others have mentioned. I grew up with rail road tracks crossing behind my parents property and have 'played' there since I was a kid. Including riding bicycles, running, atvs and dirt bikes, fishing and hunting off of them. I even used to take them to get to school and work on a Honda xr that I used to run around on.
I've never run into any issue, or had any problems.
But it sounds like that isn't the case in many areas.. so I would make some calls and find out for sure. Not worth getting in trouble for.
-Jake