no, it's not simply transplant from the 2D cab code. In 2D you change standalone textures that have a specific tratment, in 3D you use the standard scenery shape/texture coding. And moreover I wonder whether in a 3D cab a "light" feature should only change textures or really foresee one or more beams of light, which would make things quite more complicated (at least for me).
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I've gone a further step forward.
Here are the .exe files to be replaced in x.3792 to have the 3Dcab night texture applied also in tunnels
and here is the source patch. I'd like to get an OK by James on this, because it adds a couple of flag values
IMPORTANT NOTE:
11/2/2017: attachments removed because feature uploaded.