Commentary on Clauses Part 2: Investigations Section 32: Privileged and confidential information
The normal rules on confidential information and legal privilege do not apply for the purposes of the NIPSO investigating a listed authority.  Normally, a listed authority could refuse to disclose this sort of information.  However, the NIPSO can insist on seeing it in the course of an investigation.  There are safeguards for this later on in the Act.  Under section 47, information subject to legal privilege cannot be included in a report.  Under section 56, this information cannot be used in court proceedings.
Sections 49 and 50 contain further provision on disclosure of information obtained by the NIPSO in the course of an investigation.