I took a look within the file structure, and it is almost exactly like rF2. Even down to having a "Packages" folder. I didn't go in too deep. I did try a couple quick things.
If you point the rF2 Mod Manager to LMU, the tracks and vehicles will show up in there.
I tried just a straight import of an rF2 track, and while the files installed, it didn't show up in game. I didn't try a car.
If you know rF1 and rF2 modding, my thought is that they changed .rfm and vehicle classes. It isn't the "all tracks and cars". Either that, or they have the UI coded to only show those tracks. It's hard track down as they do have the new .mas encryption on all the .mas files. There hasn't been any available tools to get past it that I'm aware of. I know some rF2 cars with the new encryption have made their way to AC, so something might be possible.
I tried to go the other way (LMU to rF2), but it looks like the encrypted .mas doesn't get added to the MAStool .rfcmp maker. I think their might be a different way to make a .rfcmp, but I haven't investigated yet.