The EBA will almost certainly have some lawyers weasel words in it that mean that application of CAO 48 is not unequivocal. CASA have a whole spidersweb of exemptions that they issue. There would be a significant chance that your airline has some sort of exemption.
Basically, our system is that we get unworkable regulations that get made workable by CASA exemptions. If you have the energy, you could look here:
http://www.comlaw.gov.au/Browse/Resu...ent/CA/26/casa
The list is a bit scary. Can you image how many people in Canberra are engaged in all of this? Just because we can't make workable regulations.
The real question is, did you feel fit to fly on the Sunday? If yes, then the issue is an administrative one of whether they have cheated you out of a leave day. If the answer is no, then it might be an ombudsman / union issue.