Whenever in the judgment of the Department it is necessary as an incident to the construction of a project on the National System of Interstate and Defense Highways, including extensions thereof within urban areas, or any State highway constructed under the provisions of Section 2 of the “Transportation Bond Act”, approved July 2, 1971, as now or hereafter amended, to relocate utility facilities, wherever located and whenever constructed, the cost of such relocation may be deemed to be one of the costs of constructing such project and the Department may, on behalf of the State, pay such costs. For the purposes of this Section, the term “utility” includes publicly, municipally, privately, and cooperatively owned utilities; the term “cost of such relocation” includes the entire amount paid by such utility properly attributable to such relocation after deducting therefrom any increase in the value of the new facility and any salvage value derived from the old facility; and the term “National System of Interstate and Defense Highways” includes any highway which now is or shall hereafter be a part of the National System of Interstate and Defense Highways, as provided in the Federal Aid Highway Act of 1956, and any acts supplemental thereto or amendatory thereof.