Whenever there shall be filed with the commission any schedule stating a change in the rates or charges, or joint rates or charges, or stating a new individual or joint rate or charge or joint classification or any new individual or joint regulation or practice affecting any rate or charge, the commission shall have authority, either upon complaint or upon its own initiative without complaint, to enter upon a hearing concerning the propriety of such rate, charge, classification, regulation or practice; and, if the commission so orders, it may proceed without answer or other form of pleading by the interested parties, but upon reasonable notice, and, pending such hearing and the decision thereon, the commission, upon filing with such schedule and delivering to the public utility affected thereby a statement in writing of its reasons for such suspension, may suspend the operation of such schedule and defer the use of such rate, charge, classification, regulation or practice, but not for a longer period than one hundred and twenty days beyond the time when such rate, charge, classification, regulation or practice would otherwise go into effect; and after full hearing, whether completed before or after the rate, charge, classification, regulation or practice goes into effect, the commission may make such order in reference to such rate, charge, classification, regulation or practice as would be proper in a proceeding initiated after the rate, charge, classification, regulation or practice had become effective: Provided, That if any such hearing and decision thereon cannot be concluded within the period of suspension, as above stated, such rate, charge, classification, regulation or practice shall go into effect at the end of such period. In such case the commission may require such public utility to enter into a bond in an amount deemed by the commission to be reasonable and conditioned for the refund to the persons or parties entitled thereto of the amount of the excess, plus interest at the rate of not less than seven percent per annum, as may be specified by the commission, if such rate so put into effect is subsequently determined to be higher than those finally fixed for such utility. In specifying the applicable interest rate, the commission shall be guided by the interest rate which such public utility would in all probability have to agree to pay if such public utility at that time borrowed in the marketplace a sum of money equivalent to the amount of money the commission estimates the increase in rates will produce between the effective date of such increase and the anticipated date the rates will be finally fixed for such public utility, it being intended that a public utility should be discouraged from imposing higher rates than it should reasonably anticipate will be finally fixed as a means in effect of borrowing money at a rate of interest less than such public utility would have to agree to pay if it borrowed money in the marketplace. No such accrued interest paid on any such refund shall be deemed part of the cost of doing business in a subsequent application for changing rates or any decision thereon. At any hearing involvinga rate sought to be increased or involving the change of any fare, charge, classification, regulation or practice, the burden of proof to show that the increased rate or proposed increased rate, or the proposed change of fare, charge, classification, regulation or practice is just and reasonable shall be upon the public utility making application for such change. When in any case pending before the commission all evidence shall have been taken, and the hearing completed, the commission shall, within three months, render a decision in such case.
Where more than twenty members of the public are affected by a proposed change in rates, it shall be a sufficient notice to the public within the meaning of this section if such notice is published as a Class II legal advertisement in compliance with the provision of article three, chapter fifty-nine of this code, and the publication area for such publication shall be the community where the majority of the resident members of the public affected by such change reside or, in case of nonresidents, have their principal place of business within this state. The provisions of this section shall expire on and be of no further force and effect after the thirtieth day of June, one thousand nine hundred eighty-one, except that as to any case pending on said date in which the suspension period has expired and rates are in effect under bond such case shall be proceeded with in accordance with this section; as to any other case pending on said date, the commission shall treat the case as filed anew on the first day of July, one thousand nine hundred eighty- one, except that it shall not be necessary for any new process or notice to be served or published.