This worked last time, maybe someone will come through again! :) http://trac.adium.im/wiki/CreatingMessageStyles lists fileTransferBegan and fileTransferComplete among the possible classes used with %status%. iT was added by David in version 17, and "corrected" in version 18. Xcode can't find it in 1.5 or 1.4, and I can't find it in adium-old or anywhere google knows about. David thinks it's a bit of code that was never committed, but I wanted to see if anyone else knows about it before I pull that out of the wiki.
-- Matthew