1. Regarding code...the only code released was for multi player side of things, not single player.
2.The bones were probably omitted/destroyed along with the vertex weighting when exported from XSI (if the bones and weights are still present in the files, problem could be the max import plugin).
Just like when you import a .glm back into max, the weighting and bones are not part of the import process since the plugin was not built for that.
Going from memory, i'm pretty sure all vehicles need at least a root bone or something along those lines to work properly.