As far as I know, the PBPA still stands! When you come back to HK, you get full expat benefits. Do you honestly think that anyone would waive or negotiate that right away? Those clowns upstairs love it when these sort of 'rumors' start. Ever heard of expectation management? If everyone says 'F.. Off, there's not a hope in hell you're taking that away from us. Full stop.', then they know they've got a fight on their hands. Loiter1, your comment should have said as much.
They feed on the weak, and the weak are signing. You've gotta ask yourself, "Am I one of the weak?" If the answer is yes, then there's not a lot anyone can do for you.
If on the other hand you decide to use your backbone, along with your fellow members, then you just never know what may be possible.
Personally, I don't think many have signed. The sub-committee seem to have a good handle on things. Be patient, follow their advice. Any better ideas?