Sorry, forgot that things might be different in the US- at least life is still easy over here as far as railfanning goes. All you need to do is tell the railway police that you are a railfan and that you are taking pictures because you want to model the train. I normally tell them exactly what I know about the train and they are suprised and see that I'm not a trouble maker (SOMETIMES it helps to have a few bucks for a cigarette or a Coke that you can give them, wink-wink).
A friend of mine that goes to Germany, told me that over there, at the ticket office for around 50 Euros, you can buy a ticket to ride in the cab on certain sections.
They have an electric loco which they call a Taurus, it's so cool. It's a 40 Ton loco that goes from 0-250km/h in just over 25 seconds!!