(1) A utility which elects to proceed under the rules of this sub-chapter shall be permitted by the commission to include in its rates a cost of service which includes the following special components:

(a) All test year measures of cost shall be adjusted to reflect changes known with certainty and measurable with reasonable accuracy prior to the commission's hearing on the utility's application for increased rates, provided no such changes shall be reflected in the rates finally authorized by the commission if they occurred more than 13 months from the close of the test period used to determine the cost of service.

(b) Test year expenses which are affected by test year replacement of capital facilities used in providing service shall be adjusted so that they accurately reflect, on an annual basis, such replacement.

(c) Any costs incurred during the test year that were not adjusted pursuant to ARM 38.5.606(1) (a) , shall be adjusted pursuant to the following formula:

Costs x .45 x Consumer Price Index

(d) The rate base shall be computed on an end of test year basis.

(e) For matching purposes, test year revenues shall be restated to reflect end of year customer counts and the annualization of known changes in revenues occurring during the test year. In addition, revenues shall be restated to reflect changes known with certainty and measurable with reasonable accuracy prior to the commission's hearing on the utility's application for increased rates, provided no such changes shall be reflected if they occurred more than 13 months from the close of the test period used to determine the cost of service in the utility's filing.