Mont. Code § 75-6-321
The cost of any water supply, wastewater transportation, or treatment system acquired or constructed under the provisions of this part must be considered to include the cost of the acquisition or construction of the supply or system and the cost of all property rights, easements, and franchises considered necessary or convenient for the supply or system and for the improvements and extensions to the supply or system. Costs also include interest on bonds prior to and during construction or acquisition and for 6 months after completion of construction or of acquisition of the improvements and extensions; engineering expenses; fiscal agent and legal expenses; expenses for estimates of cost and of revenue; expenses for plans, specifications, and surveys; other expenses necessary or incidental to determining the feasibility or practicability of the enterprise; administrative expense; and other expenses that may be necessary or incidental to the financing authorized in this part, the construction or acquisition of the properties, the placing of the properties in operation, and the performance of the things required or permitted, in connection with any property.
§ 75-6-321, MCA