If you are only hanging around because of the bond, then ASA's game of deception is beating you...
Heard one guy recently requested directly to Canberra HR for a copy of his contract... and... 3 months later still no response... Given many BN and ML HR staff were somewhat left "pissed off" with the last HR staff re-alignment, I can't see the mass of bonds signed in the last 5 years having being delicately placed into a folder and carefully posted to it's new home in Canberra HR. Better luck asking Mr Shredder Machine to spit them back out maybe... Don't know about Tower bonds.
Also the story of the guy mentioned above that stayed because of his bond is not so straight-forward. Many other circumstances involved, and the bond was not the most important.
Feel free to challenge them. It's just business, nothing personal. Ask them for the orginal, not a copy - the original form that YOU signed. If you are in the union, use your "get one free" annual legal advice. Take them to the high court, as the running consensus seems to be it wouldn't hold up.
But please - let us all know how you go !!!