You can't do much with a rendering since its just a 2D image. Maybe use it as a texture, or a mask, but I don't think thats what you want.
I bet they made a tool for Black and White that imported Bryce or Autocad files into their own proprietary format, unless the data files for that game really are just straight Bryce or Autocad files.
The DXF format that Autocad pioneered seems to be pretty standard now, just about every 3D app supports it. I bet its not hard to find docs on it.