Mont. Code Ann. § 85-8-349

At any time prior to making the order confirming said report or thereafter, the court may permit the commissioners to present and file a supplemental report or amend their report as to any matter which, pursuant to the provisions hereof, was or might have been included in the original report presented by them, and after reasonable notice given to all parties interested, in such manner as the court shall direct, the court may, upon the hearing in said matter, make such order as the case may require.