Mont. Code Ann. § 69-5-106

A regulated utility electric facilities provider has the right to furnish electric service facilities to the premises of a large customer if the regulated utility electric facilities provider can extend its electric service facilities to the premises of a large customer at less cost than other electric facilities providers. The estimated connected load must be determined from the plans and specifications prepared for construction of the premises or, if an estimate is not available, must be determined by mutual agreement of the electric facilities provider and the large customer.