(1) The commission, each commissioner and each person employed by the commission shall have the right at any and all reasonable times to inspect the accounts, books, papers and documents of any public utility. The commission shall also have the right to inspect the records of a public utility’s holding company, parent, affiliate, or subsidiary that engages directly in any transaction with the regulated utility which results in expenses being incurred, allocated or otherwise attributed to regulated services of a public utility; provided however, the commission may inspect only those records which are necessary to determine whether such expense was properly incurred and should be included, in whole or in part, in the public utility’s rates.
(2)  The commission, each commissioner and any employee authorized to administer oaths shall have power to examine under oath any officer, agent or employee of such public utility in relation to the business and affairs of said public utility: provided, that any person other than a commissioner demanding such inspection shall produce under the seal of the commission his authority to make such inspection. A written record of the testimony or statement so given under oath shall be made and filed with the commission.