Mont. Code § 7-3-1212
The members of the board of county commissioners of the county and members of the council of every city and town therein holding office on the date when any election is held at which the question of the consolidation and merging of the county and city and town governments is approved and adopted by the qualified electors of the county shall continue in office and in the performance of their duties until the first commission shall have been elected and have qualified, whereupon such board of county commissioners and city and town councils shall be deemed abolished. All other persons holding offices or positions, whether elective or appointive, under the government of such county or under the government of any city or town therein at the date of such election shall continue in the performance of the duties of their respective offices and positions until provision shall be made by the commission for the performance or discontinuance of such duties or the discontinuance of such offices or positions.
§ 7-3-1212, MCA