The district may not construct or improve a public highway or public mass transit system without the approval of the Commonwealth Transportation Board and the county. At the request of the commission, the Commonwealth Transportation Board may exercise its powers of condemnation pursuant to Chapter 2 (§ 25.1-200 et seq.) or 3 (§ 25.1-300 et seq.) of Title 25.1 or § 33.2-705 for the purpose of acquiring property for transportation facilities within the district. Upon completion of such construction or improvement of a public highway, the Commonwealth Transportation Board shall take such public highway into the primary or secondary system of state highways for purposes of maintenance and subsequent improvement as necessary. Upon acceptance by the Commonwealth of the highway into the state highway system, all rights, title, and interest in the right-of-way and improvements of such highway shall vest in the Commonwealth. Upon completion of such construction or improvement of a mass transit system, all rights, title, and interest in the right-of-way and improvements of such mass transit system shall vest in the Northern Virginia Transportation Commission or other agency or instrumentality of the Commonwealth.