I have heard (3rd or 4th hand) of an anecdotal report of someone fracturing a bone while on cabo (result of a fall) and the bone healing. FWIW.
Note also that EXEL mgr has talked about bone scan hot spots caused by arthritis are unaffected. That said I think the truth is probably somewhere in the middle - certain pathways to activate bone remodeling are disabled but not others.
PS from the few bone scans they have shown with apparent arthritis it looks like there is some down reg - but nowhere the same amount as seen in mets.