Obama's on it!!!
In all seriousness, (I haven't taken a train in decades - Amtrak doesn't go anywhere that I want to!), I have read that TSA has already established screening areas for train passengers. I don't know if that is true or not, though.
Yes, I do believe that TSA is at the Amtrak stations right now. The thing is though there aren’t many Amtrak stations Nationwide.