(a) Whenever the Commission is of the opinion and so finds after an examination of any report or reports, annual or otherwise, filed with the Commission by any public utility, together with any other facts or information which the Commission may acquire or receive from an investigation of the books, records or papers or from an inspection of the property of such public utility, that the net income of such public utility after reasonable deductions for depreciation and other proper and necessary reserves, is in excess of the amount required for a reasonable return upon the value of said public utility's property used and useful in rendering its service to the public, provided however that in computing net income, deductions shall not be made for advertising expenses as prohibited under Section 9-225 of this Act, and if the Commission is of the opinion and so finds in said cause that a hearing to determine all of the issues involved in a final determination of rates or services will require more than 105 days of elapsed time, the Commission shall have the power in cases of such emergency and it is hereby given authority to at once enter a temporary order, after notice to said public utility, fixing a temporary schedule of rates, which order shall be forthwith binding upon said public utility; provided, however, that the Commission's power to order reductions in rates and charges of any public utility by means of any such temporary order, is limited to reductions which will absorb not more than the amount found by the Commission to be in excess of the amount of income as determined by the Commission necessary to provide a reasonable return on the value of the property of said public utility as found by the Commission as aforesaid; and provided, further, however, that no such temporary order shall remain in force or effect for a longer period than 9 months from its effective date, and a further period not to exceed 3 months in addition if so ordered by the Commission; and provided, further, that if upon the final disposition of the issues involved in such proceeding, the rates or charges as finally determined by said Commission or the court having jurisdiction of the subject matter are in excess of the rates and charges prescribed in said temporary order, then and in such event such public utility shall be permitted over such reasonable time as the Commission shall fix, to amortize and recover by means of a temporary increase over and above the rates and charges finally determined, such sum as shall represent the difference between the gross income obtained from the rates and charges prescribed in said temporary reduction order and the gross income which would have obtained, during the period such temporary reduction order was in effect, based upon the same volume, from the rates and charges finally determined.(b) If the Commission enters upon a hearing concerning the propriety of any proposed rate or other charge, classification, contract, practice, rule or regulation pursuant to Section 9-201, and if the Commission is of the opinion and so finds in said cause that a hearing to determine all of the issues involved in a final determination of rates or services will require more than 120 days of elapsed time, the Commission shall have the power to enter a temporary order fixing a temporary schedule of rates after hearing, which order shall be forthwith binding upon the public utility. As soon as practicable after the effective date of this amendatory Act of 1985, the Commission shall determine by rule the facts and circumstances which must be established by the utility in order to justify the grant of a temporary rate increase as provided herein. The Commission shall determine any temporary rate increase according to previously established standards until the time such rules become effective. In any case in which the Commission grants interim relief, the Commission shall, upon final disposition of the proposed permanent change in rates or other charges, classification, contract, practice, rule or regulation, also review the propriety of its prior award of interim relief based upon the criteria used by the Commission in granting the interim rate relief. If, upon such review, the Commission determines that such interim rates or charges were in excess of the rates or charges which should have been prescribed in its temporary order, the Commission shall require the public utility to refund such sum as shall represent the difference between the gross income obtained from the rates or charges prescribed in said temporary increase order and the gross income which would have been obtained during the period such temporary increase order was in effect based upon the same volume, from the rates and charges which the Commission upon final review determines were appropriate. Any refund shall include interest calculated at a rate determined by the Commission and shall be returned according to procedures prescribed by the Commission.