TG2 does not integrate directly with Xfrog, but models in OBJ and TGO format are compatible with TG2. I don't know the capabilities of the Xfrog software for C4D, but I would assume you could export to OBJ since C4D can do so. If you can get a model into OBJ format, it is compatible with TG2. If you have additional Xfrog-specific questions, it's best to ask Xfrog or their user forum about them.
TG exports geometry in standard formats (OBJ and LWO) that nearly every 3D app is compatible with. Likewise TG imports OBJ data, which most apps support. For camera information, TG only currently imports the Nuke CHAN format, which some other 3D apps do support. I don't know the specific capabilities or plugins of all the 3D apps, but I've seen users having success with Maya, 3DS Max, and others. There is a plugin for 3DS Max that makes data exchange a bit easier between TG2 and Max, so that could be a compelling factor, but other than that most 3D apps are equally easy to integrate with TG2 since generally standard formats are used.
- Oshyan