Mont. Code Ann. § 7-12-2169

All costs and expenses incurred in any improvement district in the acquisition, construction, or maintenance of any improvement specified in this part or incurred in the issuance of bonds or warrants of the district, including incidental expenses, shall be paid for by special improvement district bonds or warrants. The board of county commissioners shall provide for making payments for maintenance or improvements in any rural improvement district by the method provided in 7-12-2172 and 7-12-2173.