PDX...
While I wholeheartedly agree with you with the ticket in hand policy...try going into the Robertson tunnel and try waiting for that right moment and placement to take a photo. Been there, had it happen to me.
Even with valid/unexpired tickets and WRITTEN permission to take photos of the Metro in LA a few friends and myself we were still hassled to the point we were asked to show our photo ID, then have a supervisor come down to chat with us.
Happened again....differnt time and place...
A friend of mine shot this at LAUS. His comments are, "I was given permission to take photographs by the folks at Metrolink and Metro as long as I didn't us a tripod and I had a valid ticket. These guys still didn't like the idea. They harrassed me for a few minutes and then I got on my train"
Good luck for anyone out there attempting this and expecting not to get hassled.