Mont. Code Ann. § 72-3-523

Except as otherwise ordered in formal proceedings, the probate of a will subsequent to the appointment of a personal representative in intestacy or under a will that is superseded by formal probate of another will or the vacation of an informal probate of a will subsequent to the appointment of the personal representative under the will does not terminate the appointment of the personal representative although the personal representative's powers may be reduced as provided in 72-3-304. Termination occurs upon appointment in informal or formal appointment proceedings of a person entitled to appointment under the later assumption concerning testacy. If a request for new appointment is not made within 30 days after expiration of time for appeal from the order in formal testacy proceedings or from the informal probate changing the assumption concerning testacy, the previously appointed personal representative upon request may be appointed personal representative under the subsequently probated will or as in intestacy, as the case may be.