(1) The public service commission may investigate, in the manner set forth in section 7, a public utility subject to its jurisdiction pursuant to Act No. 3 of the Public Acts of 1939, as amended, being sections 460.1 to 460.8 of the Michigan Compiled Laws, the motor carrier act, Act No. 254 of the Public Acts of 1933, as amended, being sections 475.1 to 479.20 of the Michigan Compiled Laws, and the Michigan telecommunication act, Act No. 179 of the Public Acts of 1991, being sections 484.2101 to 484.2605 of the Michigan Compiled Laws, which the commission believes has engaged, is engaging, or is about to engage in a method, act, or practice which is unlawful under this act.

    (2) When the commission requires the use of the subpoena power provided in this act, an application shall be made to the attorney general who shall procure a subpoena on behalf of the commission in accordance with section 7.

    (3) Upon conclusion of an investigation, the commission shall provide a full report to the attorney general.