Mont. Code Ann. § 20-3-312

The trustees of any district to which the territory of another district is attached as a result of annexation, abandonment, territory transfer, or any other method of changing district boundaries, except by the reorganization of districts under 20-6-423, continue to be the trustees of the district with the same powers, duties, and responsibilities and subject to the same limitations provided by law as if there had been no boundary change. In the case of district reorganization, the appointed trustees of the resulting district shall assume their trustee positions under the authority of 20-6-423.