As a Massachusetts native and somewhat frequent user of the absolutely fantastic public transportation system, I have created MBTA skins for BeamNG. I used actual examples of various MBTA vehicles and turned them into the skins and made them as best as I could for the vehicles. The only issue is the D-Series skin shows missing textures, I will figure this out. Otherwise, it's pretty fantastic.
MBTA's The Ride
MBTA Transit Police New/Old livery
MBTA Utility Truck
MBTA Silver Line