It appears to read and or write to and from DWG, and DGN.
I think that IF you specify a deliverable from these folks that includes BOTH the DWG for the features, and and XML file of the terrain model you should have no major issues using the data they produce.
Otherwise, the FILE format is of no concern to you should they be able to provide an FBK file, and or and ASCI point and fault line file for you to import into C3D.