427. An inspector authorized by the court to conduct an investigation is to that end vested with the powers and immunity of commissioners appointed under the Act respecting public inquiry commissions (chapter C-37), except the power to order imprisonment. No person is excused from giving evidence or producing documents to an inspector by reason only that the evidence tends to incriminate that person or subject that person to any proceeding or penalty. However, no such evidence may be used or is receivable against that person in any proceeding under any Act, other than a proceeding for perjury or for the giving of contradictory evidence.