Except as provided in the plan and any subsequent plans, a company that has an alternative regulation plan approved under section 237.764, is not subject to the rate-of-return regulation or earnings investigations provisions of section 237.075 or 237.081 during the term of the plan. A company with an approved plan is not subject to the provisions of section 237.57; 237.59; or 237.60, subdivisions 1, 2, 4, and 5, during the term of the plan. Except as specifically provided in this section or in the approved plan, the commission retains all of its authority under section 237.081 to investigate other matters and to issue appropriate orders, and the department retains its authority under sections 216A.07 and 237.15 to investigate matters other than the earnings of the company.