Seems I've answered my own question
When I export a terrainobject in Bryce the materials are saved as mtl-files. Importing the terrainobject in TG2 there is a multishader attached to it with, in my case, one material.
The material doesn't get loaded automatically, but this has to be done by hand: find the mtl-files;
Bryce saved another file as a material file (Amorphium 3 material), but when I use that I get an error message in TG2.
Hope this may be helpfull for someone else too...