As far as anyone knows (BASSA have been suitably vague - witness the question on the ballot paper), removal of the "imposition of new crewing levels" would stop the ballot.
I would suggest that BASSA would like "New Fleet" to be taken off the table (fat chance now, I reckon) but they can't make it a condition of calling off the strike because it hasn't happened yet and you can't strike about something which "may" happen in the future (ok, we all know it's going to happen but until the first person is recruited to "New Fleet", BASSA can't do anything about it. It would also require a new ballot at that point).
Edit: BASSA2010, love the location by the way. If only the real LA resident had half a clue.... 