OK, this post is a bit of a stretch but it *is* subway and commuter rail related. Here's a photo taken today of a "T" license plate on what I'm guessing is a generator or air compressor. This plate appears on city buses and on cars for "The Ride" -- some sort of an automobile service to fill in where the transit system (trains; subway i.e.,"The T"; and buses) don't go.
This photo was taken in Ayer, Massachusetts on the north side of Pan Am (Guilford)/Norfolk Southern double tracks that support both the Massachusetts Bay Transportation Authority (MBTA) commuter rail and the aforementioned freight lines. There's something interesting going on along those tracks, which I'll post separately under Real Trains.
The Ingersoll-Rand tow-able whateveritis has single axle trailer-style tires and front and rear rail wheels, so it clearly can ride the rails. Notice the blue speck in the distance in the shot below. The bonus surprise is a leased CIT engine 3809, a GP38-3:
Here's the CIT parked on a siding while the commuter rail heads west toward the Ayer platform.
While this plate isn't a vanity plate per se, it is subway/commuter rail MOW related, which got me poking around the internet. The MBTA plate also came in the prior green color (internet photo):
The Massachusetts Transit Authority, which predated the MBTA, had an austere black plate -- almost Puritanical (internet):
Lastly, the Transit Police have their own plates. Here's number one (internet) and an example of a transit police car (Wikipedia) with an updated version:
Got any transit or transit police plates to post from your neck of the woods?
Tomlinson Run Railroad