Mont. Code Ann. § 7-3-1210

All contracts entered into by the county or by any city or town therein or on behalf of any improvement district by such county or by any such city or town prior to the election and qualification of a commission under this part and part 13 shall continue in full force and effect subsequent thereto. Public improvements for which initial steps may have been taken under laws effective in the county prior to the election and qualification of a commission under this part and part 13 may thereafter be carried to completion in accordance with the provisions of such laws.