There is some control the artist has over the vehicle lights (specifically the brightness), but these are set in the materials, which I think are crunched and inaccessible without a re-export of the vehicle, which requires the original setup file. Unfortunately even then we don't have control of the brightness of the tail lights (I believe it's either half or 75% the full brightness of the brake light, and hard coded as such), or the speed of flashing for emergency lights, turn signals and the like. The glares that go along with those lights are created by the effects department, but I think they are locked into the same flashing pattern as we are for the sake of consistency (if not then it may also be hard baked into the effect data rather than a table).
We had potential control over all those elements through tables in RFA, but there was never any call for that level of control on SR so the system never made the jump (as Rob notes, RF lights and SR lights work very differently, so they weren't inherently compatible).