What do you mean with "recognised by the game as such"? Ultimatey it's a .GR2 mesh with a DDS texture / normal. You import it into the game as "scenery" by adding the mesh, the texture and then creating a new material combing the mesh and the texture. So far I haven't had any problems (like UV mapping, etc...) with any model.
If you want to use character models with animations, you need to edit / add a rigged skeleton, such that it maps to Larians animation system. I don't have gathered infortmation on that yet though, but I guess someone from Larian might provide input about that soon.
