I use 3D Studio Max and have no working knowledge of C4D, but in Max there's a good plugin which imports camera and light information from TG scene files. You can also import lwo geometry out of TG, but I wouldn't use that, as it exports millions of unconnected triangles even at low render settings. Instead I would export a heightfield map out, by connecting your landscape through a new heightfield generate shader, then right click and save that to a .ter, import that into Max, then tweak the displacement looking through the imported camera until I get it lined up. If for some reason, like plant populations, that doen't work, then you could use a low poly lwo export then use that as a template to push pull vertices on a plain in the 3d ap to get things to line up.
But my favoured way is to ignore the camera projection aproach completely and just take the camera out of the 3d app and bring it and it's animation into TG then stick it on the farm over night. Way more flexible interms of limited perspective shift you'd get from projection, just takes longer to render. That's if I can't just get away with a sky box, or a background still plate.
Sorry I know this doesn't answer your question for C4D, but it may give you a steer on what to look for when working out your solution.
* just seen Falcons reply, which will also need some tweakage to get right with the conversion from black to white into real terms that you can dial into C4D, but definately workable.
