I have asked casa under the foi act for my entire case,I bet I do not get all of it.because then we will see the truth and extent that they went to.
Did you look at seeking a review of the AAT decision or an appeal? If it goes to the Federal Court you can subpoena the documents but of course you face further risks as to costs if it goes against you.
Perhaps you should also be briefing the Commonwealth Ombudsman at this point as well?
Good luck
kaz