The parliamentary privilege, whether it is to send for records and papers, to compel the production of documents or to send for witnesses, exists to support the function of the House as the grand inquest of the nation and the investigative power function of the House of Commons and its committees.
Other parliamentary privilege exists to protect the House and its members from outside interference. Parliamentary privilege does not exist so that the House can assist outside powers like the judiciary or police forces to conduct their functions. As I stated, as a matter of parliamentary law, when witnesses testify before committees or when submissions or documents are produced, there is immunity protecting the witnesses, and these proceedings are not admissible before a court of law.
Traditionally, there is always a separation between various powers in Canada. I think this very committee set the gold standard about 20 years ago when, during the sponsorship scandal, there was one witness who was called upon to testify before the committee while there was also a police investigation into that person. The committee, so as to not interfere with the police investigation, decided to hold the meeting in camera for the very reason that they did not want to interfere with the police investigation, and it kept those proceedings in camera for a number of years so as not to interfere with the investigation.