For QTAC, people know they qualified for multiple offers (but I don't think actually received multiple offers) by putting UQ or Griffith first, but getting a congratulatory phone call (but no formal offer in the end) from JCU.
They get a phone call from JCU and if they don't decline over the phone (I imagine very few would!) they receive a formal JCU letter of offer in the mail. This is even when they have UQ/Griffith at a higher pref. Then if qualified for UQ/Griffith they also get this offer from QTAC a few days later.