Oregon Revised Statutes Utility Regulation § 756.538

(1) In any investigation, the Public Utility Commission may take the testimony of any person by deposition upon oral examination or written interrogatories for the purpose of discovery or for use in the investigation.

(2) In any proceeding requiring a hearing, the commission or any party to the proceeding may take the testimony of any person by deposition upon oral examination or written interrogatories for the purpose of discovery or for use as evidence in the proceeding, or for both purposes.

(3) Depositions may be taken within or without the State of Oregon by the commission, or any other person authorized to administer oaths, in accordance with procedures prescribed by the rules of the commission.

(4) The commission shall promulgate rules concerning the manner of applying for and taking depositions and the use thereof. Such rules shall provide reasonable provisions against abuse of such procedure and for protection of the rights of all persons affected.