Currently export of terrain data through built-in (i.e. purpose-built) tools is limited to heightfield and terrain geometry export. You can export heightfields in Terragen TER format or OpenEXR. You can export geometry in LWO, OBJ, and now FBX as of 2.5 (licensed version only). Exporting texturing/color data, etc. is not natively supported, but can essentially be done using orthographic camera, flat lighting, and standard renders. But it's not ideal, and won't be UV mapped to the terrain geometry.
- Oshyan