(1) A portion of the net income of taxpayers engaged in the transportation of freight or passengers within and without Montana may be attributed to the movement of revenue-producing equipment, drivers, train crews, or other operating personnel across the state.

(2) The percentage of miles traveled within Montana to total miles traveled everywhere shall be the percentage used in determining the amount of income attributable to this state. The apportionment formula for such transportation companies shall be computed as follows:

(a) Fixed properties, such as buildings and land used in the business, terminal facilities, shop equipment, and cars and trucks used in gathering or delivering local freight, shall be assigned to the state in which such properties are located. The value of equipment used in interstate transportation shall be assigned to this state on the mileage basis.

(b) The wages and salaries of employees assigned to fixed locations as officers or clerical, administrative, pickup and delivery, or terminal personnel within this state shall be included in the Montana payroll factor. The wages of personnel operating transportation equipment within and without this state shall be assigned to this state upon the basis of miles. The wages of such personnel shall be assigned to Montana in proportion that miles traveled within this state bear to the total miles traveled everywhere.

(c) Revenues will be assigned to this state in the proportion that the miles traveled within the state bear to the total miles traveled everywhere. All other revenue shall be assigned in accordance with the provisions of 15-31-310 and 15-31-311, MCA, and ARM 42.26.251 through 42.26.259.