Whenever there shall be filed with the division of motor carrier and railroad safety by any motor carrier any schedule stating a new individual or joint rate, fare or charge, or any new individual or joint classification, or any new individual or joint regulation or practice affecting any rate, fare or charge, the division shall have, and it is hereby given, authority, either upon complaint or upon its own initiative without complaint at once, and if it so orders without answer or other formal pleading by the interested carrier or carriers, but upon reasonable notice, to enter upon a hearing, concerning the propriety of such rate, fare, charge, classification, regulation or practice; and pending such hearing and the decision thereon the division, upon filing with such schedule and delivering to the carrier or carriers 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, fare, charge, classification, regulation or practice, but not for a longer period than one hundred and twenty days beyond the time when such rate, fare, charge, classification, regulation or practice, would otherwise go into effect; and after full hearing, whether completed before or after the rate, fare, charge, classification, regulation or practice goes into effect, the division may make such order in reference to such rate, fare, charge, classification, regulation or practice as would be proper in a proceeding initiated after the rate, fare, charge, classification, regulation or practice had become effective; provided, that if any such hearing cannot be concluded within the period of suspension, as stated in this section^*, the division may, in its discretion, extend the time of suspension for a further period not exceeding six months. At any hearing involving a rate increased or a rate sought to be increased after August 28, 1996, the burden of proof to show that the increased rate or proposed increased rate is just and reasonable shall be upon the motor carrier, and the division shall give to the hearing and decision of such questions preference over all other questions pending before it and decide the same as speedily as possible.