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