Possible however not allowed and requires great skill and knowledge of the LFS code (I guess). Kegetys the über legendary OFP/RBR/ArmA/LFS addon coder imported a fully working Mclaren F1 a few years ago.
Well, as far as I know, kegetys isn't banned for it so I'm guessing it is ok but you aren't allowed to tell anyone how to do it or release that kind of mod to the public.
He definately delivers useful work with a high standard. I don't know about all his work but I'm especially impressed with his SoftTH. This takes 'modding' to a whole new level. I could imagine corporations developing this type of program with less functionality, more restrictions, less performance, worse quality and asking major fees.
Anyway at some stage importing cars ect would be looked at which then would see if it was feasible to apply and whether it would be worth it, which at a guess a public vote may happen which i strongly doubt would.
Custom cars and tracks would take away from LFS uniqueness therefore making it another run of the mill racing sim which i doubt anyone wants.