The department, either solely or in conjunction with a city, county, or consolidated local government, shall pay the costs of construction of streets, curbs, gutters, and sidewalks and maintenance of streets, highways, curbs, and gutters that are: (1) state highway routes; and (2) within incorporated municipalities.
Payment Of Construction And Maintenance Costs Within Municipalities
Mont. Code Ann. § 60-2-210, under Department of Transportation General Powers and Duties.
Mont. Code Ann. § 60-2-210