I think officially they are still required to be worn in the room, but in reality I haven't heard of any SCA requiring them to be worn in the room with the door closed. On a recent trip on the Silver Meteor, my SCA said he didn't care whether I wore it in the room with door closed or open. I even forgot to put it on once or twice when going into the diner for a cup of coffee to go, and no one said a word.
If you get a stickler SCA, you can just close and lock the door and close the curtains on the aisle windows, and no one will know the difference. Just have it ready to whip on when there's a knock at the door.
I don't know how crowded the diner is on the EB with traditional dining. On the Meteor with Flex dining, there were always plenty of empty tables available.