Many years ago, the community received a bunch of official Trespasser assets. Among these files were an early version of Plains in 3ds Max format. Sadly this file only had foliage and the Block House, but not terrain, or textures.
The last few weeks, our forum member Draconisaurus have worked hard to make a terrain based on the height of the objects found in this 3ds Max scene. The result is really nice and it gives you an insight of what the level might have been at one point.