I was busking at Porter, and an MBTA Transit Police Officer was on the platform with a clipboard, apparently just tracking numbers of how many people were using the station during that time period.
(I assume that's what they're doing. I figure if it were anything important, like an unauthorized LED, there would be at least five police officers and three police cars using all kinds of cop equipment that they had hanging around the police officer's station. I don't know why other T employees can't do this type of work, but I know little of the ways of the T.)
Anyway, when the officer was done, she walked over and tipped me a couple bucks. I always like when T employees tip me. Makes me feel like I probably won't get kicked out of that station that day.