Mont. Code Ann. § 20-10-105

When the residence of an eligible transportee is a matter of controversy and is an issue before a board of trustees, a county transportation committee, or the superintendent of public instruction, except as provided in 20-9-707, the residence must be established on the basis of the general state residence law as provided in 1-1-215. Whenever the state is determined to be responsible for paying tuition for any pupil in accordance with 20-5-321 through 20-5-323, the residence of the pupil for tuition purposes is the residence of the pupil for transportation purposes.