The maps are stored in the .bins, which are serialized forms of text files that the client is also able to load. The maps refer to geos, which contain the vertex buffers and textures needed to produce the geometry for various objects, as the name suggests. There are also "Fx" that produce dynamic visualizations, but I've not delved much into those.
You're not the only one in this boat: even internally Titan Network has done little more than decode a roof-mounted air conditioner model just as a proof of concept.