I asked Pegasus about VaultWiki -> MediaWiki prior to my finding XenCarta, he suggested I get a developer to reverse engineer the MediaWiki -> VaultWiki script.
That said, there are only 4 tables in XenCarta, EWRcarta_ cache (which rebuilds itself), EWRcarta_history, EWRcarta_templates and EWRcarta_pages.
I reckon you could write an insert to migrate your VaultWiki "threads" into the EWRcarta_pages table and see what happens.....
The few pages of yours I looked at seemed to be using pretty generic BBCode, my issue was with all the complex tables in VaultWiki.