Which static vehicles are you looking for? They'll be found in the Sceneryobjects folder, you may have to do some digging to find them. I remember looking into them a while back (it was the SD202) and it's no different than creating a repaint for a drivable bus.
If you're looking for the C400, it's found here:
Code:
Sceneryobjects\UKDT\BotW\London Citybus 400 Static (Devon)\texture
Just edit/replace Exterior_static.png.
(Also, if you're interested, I could send you my First Greater Manchester logo if you want.)