The RBA is bound by the Reserve Bank Act 1959, and while the bank has certain freedoms to direct monitary policy, it must report to the treasurer and in matters of disagreement the Governor General can intervene and if need be force the bank to implement changes to its policy, so the RBA isn't a law unto itself (perhaps more akin to a stubborn teenager who will direct all efforts towards trying to get away with whatever it can and never admit to being wrong). It is important to distinguish the RBA from the US Federal Reserve, because as I understand while the Fed Act Section 31 reseves the right to amend or revoke the Act by Congress, there doesn't appear to be anything about accountability beyond reporting to Congress (Congress doesn't appear to be able to overrule policy without amending the Act, wheras in Australia there is a legislated procedure for disagreements).
sources: http://www.rba.gov.au/about-rba/accountability.html#consultation_with_government
http://www.federalreserve.gov/aboutthefed/section31.htm