(1) A utility filing for a general rate increase may elect to make its filing under this sub-chapter, provided such election is made within 24 months of the publication of the notice of adoption of the rules of this sub-chapter. Such election shall be binding and irrevocable for a period of 71 months after the date of such filing, subject to the provisions of ARM 38.5.605. The utility's election to proceed under this sub-chapter shall be contained in its initial filing and shall provide, without qualification, that:

(a) The utility elects to process its filing under this sub-chapter, and that it consents to having the rates it is authorized to charge for the utility's services under consideration determined in accordance with this sub-chapter for a period of 71 months from the date of the filing in which it made its election, subject to the provisions of ARM 38.5.605.

(b) The utility will file with the commission, at intervals of 24 and 48 months after the date of the filing in which it made its election, a complete cost of service filing pre- pared in accordance with the commission's rules, including the rules of this sub-chapter.

(c) The utility will file with the commission 72 months after the date of the filing in which it made its election, a complete cost of service filing prepared in accordance with the commission's rules, excluding the rules of this subchapter. Nothing in this rule shall be construed as prohibiting the utility from simultaneously applying to the commission for authority to establish rates in the same manner as set forth in this sub-chapter, or any other manner.

(d) The filing requirements specified in ARM 38.5.604(b) are intended only to establish a minimum frequency of filings. Nothing in these rules shall be deemed to prohibit a utility, or any other party, from making application to the commission for additional rate changes. Except in the case of a filing pursuant to ARM 38.5.604(c) , additional filings will be prepared in accordance with the commission's rules, including the rules of this sub-chapter.