License plate issue is interesting. Are there any flipped normals there?
As for the lights, what I imagine you need to do for that realistic look is tae the light texture (hoping it has a plastic light texture) and create a mask with it. I think one way you could do this is feeding the textures into Materialize and create a custom AO map which represents the plastics diffusion of light, and use that to mask the luminosity, hoping ti creates a look of light glowing through the plastic. A reflection layer over that for plastic reflection could help with any stronger light sources, like during the day.
If the textures don't have enough detail you could use hard "luminosity" grayscale mask to then composite in some plastic texture which could then be used in something like Materialize to generate some maps for it (mainly disp/bump) to then use the AO feature.
I only suggest this look because I notice with (at least cloaded-ish car lights) that the light directly around out-ward geometry seems to have less light transmitting through. This is probably caused by the rough textured back of the plastic lens which is refracting light waves.
