Mont. Code Ann. § 7-13-3018

Whenever any lot, piece, or parcel of land belonging to the United States fronts upon the proposed work or improvement or is to be included within the district, the governing body shall in the resolution of intention declare that the lots, pieces, or parcels of land must be omitted from the assessment to be made to cover the cost and expenses of the work or improvement, and the cost of the work or improvement in front of the lots, pieces, or parcels of land must be paid by the local government from its general fund.