220 ILCS 5/10-108
Complaint may be made by the Commission, of its own motion or by any person or corporation, chamber of commerce, board of trade, or any industrial, commercial, mercantile, agricultural or manufacturing society, or any body politic or municipal corporation by petition or complaint in writing, setting forth any act or things done or omitted to be done in violation, or claimed to be in violation, of any provision of this Act, or of any order or rule of the Commission. In the discretion of the Commission, matters presented by one complaint may be ordered separated, and matters upon which complaint may be founded may be joined. No objection shall be sustained to a separation merely because the matters separated are under the ownership, control or management of the same persons or corporation. No complaint shall be dismissed because of the absence of direct damage to the complainant.
Upon the filing of a complaint the Commission shall cause a copy thereof to be served upon the person or corporation complained of which shall be accompanied by a notice requiring that the complaint be satisfied and answered within a reasonable time to be specified by the Commission or within the discretion of the Commission, by a notice fixing a time when and place where a hearing will be had upon such complaint. Notice of the time and place shall also be given to the complainant and to such other persons as the Commission shall deem necessary. The Commission shall have authority to hear and investigate any complaint notwithstanding the fact that the person or corporation complained of may have satisfied the complaint.
The time fixed for such hearing shall not be less than ten days after the date of the service of such notice and complaint except as herein provided. Service in all hearings, investigations, and proceedings before the Commission may be made upon any person upon whom a summons may be served in accordance with the provisions of the Civil Practice Law and all existing and future amendments thereto and modifications thereof and the Supreme Court Rules now or hereafter adopted in relation to that Law, and may be made personally, by electronic means, or by mailing same in the United States mail in a sealed envelope with postage prepaid. The provisions of this section as to notice shall apply to all hearings held by the Commission or under its authority.
Any public utility shall have a right to complain on any of the grounds upon which complaints are allowed to be filed by other parties, and the same procedure shall be adopted and followed as in other cases.
All cities shall have power to appear as complainants or to make application before the Illinois Commerce Commission for an inquiry, investigation or hearing relating to the rates or other charges or services of public utilities within such city; and in case of any inquiry, investigation or hearing by or before the Illinois Commerce Commission on any matter relating to the rates or other charges or services within any city, the city shall receive written notice not less than ten days before such inquiry, investigation or hearing, and shall be entitled to appear and present evidence relating to the subject matter of such inquiry, investigation or hearing. Such notice shall be served upon the city clerk.
Whenever there shall be filed a complaint under Article IX of this Act regarding the rates, charges, classifications or services of a public utility, the Commission shall make and render findings concerning the subject matter and facts complained of and enter its order based thereon not later than one year after the filing of such complaint unless all parties to the complaint proceeding under Article IX agree to a period of greater than one year, provided that any agreement to extend the one year period must be in writing and must be for a specified period of time not exceeding 60 days. The parties may enter into more than one agreement to extend time.
In the event that the Commission fails to enter its order within one year after the filing of the complaint or upon the expiration of the last agreement to extend time, any party may file a complaint in the circuit court for an emergency order of mandamus to direct and compel the Commission to enter its order within 60 days of the expiration of the one year period or within 60 days of the expiration of the last agreement to extend time, and the court shall set a schedule to enable the Commission to complete the case and enter an order within the time frame specified herein. Summons upon the complaint shall be returnable within 5 days. The complaint for an order of mandamus shall be brought in the circuit in which the subject matter of the complaint is situated or, if the subject matter of the hearing is situated in more than one circuit, then in any one of those circuits.
220 ILCS 5/10-108