Had a similar run in at DC Union Station with a MARC employee, on P877, Brunswick line, three years ago. At the time I was returning home from my job as an editor for a Washington Post newspaper at the Navy Yard. Was on the platform when the conductor, [name redacted] threatened to arrest me for photographing one of the new MP36 engines that was on the platform next to my train, claiming that, "I would post the picture online where it could be accessed by terrorist".
I then stated Amtrak's policy pertaining to photography at DC Union and even pulled out a copy of the document to which he replied, he would have me arrested by Amtrak police for trespassing, despite having a valid monthly ticket. I informed him that he will also miss his train as I will personally ensure he is held by the police as well while we worked this out with the appropriate Amtrak and MARC management.
Now, mind you, I had a small laptop bag on my shoulder, and a little Fuji X100 camera with me. (as opposed to my full-size Nikon D3s with all that huge f/2.8 glass), so it was not as if I had a huge monster professional camera or anything more han even a normal tourist wouldn't carry.
Not sure if either my Navy issued WaPo press credentials were showing, or my NARP ambassador badge was visible, but he decided not to call it after a stern warning after noticing something on my messenger bag. Since, I was already having a bad day, I decided I was sick of my rights being stepped on again in DC for doing my job and wasn't going to let it go, so easily.
On the train, I got his name, and immediately contacted Malcom Kenton, NARP (I serve as an ambassador at the NARP booth at Union) as well Mickey Osterreicher, General Council for NPPA. Needless to say, by the time I got to Point of Rocks, both Amtrak, and MARC were investigating as well as the yard master for Union.
By the end of the week, I had received calls from Amtrak HQ offering an official apology, and then from MARC with an apology along with stating that the conductor who is now retired was sternly reminded by MARC that even as a CSX employee he must follow Amtrak policy at DC Union.
Long story short, I did seven years in the Coast Guard before going to WaPo so I've been on the other side of the whole terrorism thing in DHS, but at the same time, I do not recall ever signing off on my rights not to be harassed either for the hell of it. It saddens me to think what will happen if there ever was another attack, because it people were really willing to give up their freedoms that first year after 9/11; people will do the same thing again.
It's become a sad time to be a railfan.
But, it's not all bad news either. A year later, I had a trip to Pittsburgh, and not only did I have no trouble getting a picture of my train, but station staff and employees jumped in with big smiling faces and wanting to be in the picture.