All powers and duties of the commission heretofore set forth in this Division 136 may be exercised within the municipalities constituting the commission and in contiguous territory not more than 3 miles beyond the corporate limits of such municipalities and in the territory necessary to interconnect any of the municipalities constituting the commission. The commission shall keep proper accounting records which records shall be kept so as to show the book value, reserve for depreciation, revenue and expenses broken down as to type of utility and by all municipalities making up the commission.
65 ILCS 5/11-136-9