As long as I can remember, the MTA crew has been putting in massive amount of work. I remember back in the day seeing SK8 MTA tags on the bus. I have not seen it personally, but I heard that MTA has the largest letters on the Los Angeles River. Even larger than the Saber piece.
Siez MTA Dreks (This is at the Plant Nursery Lot)
MTAliens Video starring Toro, Sufer and Hilo from MTA