Twin NDB - This piece of legistlation does give the executive director of the ATSB the power to deem information gained from an OBR to no longer be legally classified as an OBR recording.
Section 49 of the legislation
49 OBR ceasing to be an OBR under Executive Directors declaration
(1) The Executive Director may, by published notice, declare that a recording, or a part of a recording, identified in the notice is not to be treated as an OBR on and after a date specified in the notice.
Now have a look at sections 54 & 55.
54 OBR information no ground for disciplinary action
A person is not entitled to take any disciplinary action against an employee of the person on the basis of OBR information.
55 OBR information not admissible in criminal proceedings against crew members
OBR information, and any information or thing obtained as a direct or indirect result of the use of OBR information, is not admissible in evidence in criminal proceedings against a crew member (other than proceedings for an offence against this Act).
To me, this means that if the executive director invokes section 49 on your OBR then you are no longer covered by section 54 or 55 as your OBR is no longer legally classified as an OBR. Thus, bringing in the possiblility of a FDR/CVR recording being used against you.
It's an unlikey case I grant you, but still possible.