Mont. Code Ann. § 70-17-106
Extent of servitude
70-17-106 . Extent of servitude. (1) Except as otherwise provided in 23-2-312 , 23-2-322 , and this section, the extent of a servitude is determined by the terms of the grant or the nature of the enjoyment by which it was acquired.
(2) A servitude granted, either by the terms of the grant or by the nature of the enjoyment, to a local, state, or federal government body for administrative purposes does not create a right to use the servitude for any other purpose unless specifically provided for in writing in the grant.
(3) The holder of a written servitude may not use the servitude to grant additional rights and privileges to a successor or assignee unless the successor or assignee is specifically provided for in writing in the grant.