Given that the exact same question is the current top post but for driving instead of transit, I feel this question was needed.
My answer: I saw some guys hooking up a Raclette Grill to the outlet in an otherwise empty German intercity rail waggon. They had it unpacked in one of these 4 person seats with a small table. No idea if that could work or if draws too much power from the board net. I just headed on to the next waggon.
It worked because cops are terrified of MPs. They know that the MPs can and will treat them the way they treat the normal citizenry.