Oh.
You know, from my understanding of how models work that seems a bit unlikely.
Why would you even make a special under-the-desk model?
What you have to understand about FNaF 1 and 2's engines is that they are barely engines. The games are really nothing more than pre-rendered backdrops with triggers placed around the place.
For example, when something grabs you in FNaF, it is not an object in the world lunging at you, but a pre-rendered
cut-scene. That's simple enough to understand, bu now you have to realize that that's how the
entire game works. All places in the office, in the building, all with the Bots or without them is a separate render.
So, because they are all renders, they are not affected by light (For the record, there is no light, either; it just loads another render), so to make things look proper, you would have to recreate each model in the conditions that are in the area, and so you remake (Or recolour) the renders.
An easy way to think about it is that it's just a series of pictures and short animations attached to triggers. There is no 'game world' or any objects in it, just pictures of them.