As per:
Parliament of Australia: House of Representatives: Appearing as a witness at a parliamentary committee hearing
In camera (private) hearings
If before the hearing a witness considers that information to be provided by the witness or requested by the committee is confidential, the witness can request that the evidence be heard in camera. If the request is granted by the committee, the public and media will be excluded from the hearing. The Chair or any member of the committee also may request that the hearing be in camera, particularly if the evidence adversely reflects on a third person or is subject to legal proceedings.
While in camera evidence is treated as secret when it is heard, the committee has the power to publish the evidence at a later date if the circumstances warrant such action. If the committee gives an undertaking to the witness that in camera evidence will not be disclosed, such evidence would only be released by the committee with the written agreement of the witness.
The big question, though. Hasn't the hearing already begun wrt Joyce and Buchanan's statements?