All assessments of real estate and tangible personal property shall be at their fair market value, to be ascertained as prescribed by law. The General Assembly may define and classify real estate devoted to agricultural, horticultural, forest, or open space uses, and may by general law authorize any county, city, town, or regional government to allow deferral of, or relief from, portions of taxes otherwise payable on such real estate if it were not so classified, provided the General Assembly shall first determine that classification of such real estate for such purpose is in the public interest for the preservation or conservation of real estate for such uses. In the event the General Assembly defines and classifies real estate for such purposes, it shall prescribe the limits, conditions, and extent of such deferral or relief. No such deferral or relief shall be granted within the territorial limits of any county, city, town, or regional government except by ordinance adopted by the governing body thereof.

So long as the Commonwealth shall levy upon any public service corporation a State franchise, license, or other similar tax based upon or measured by its gross receipts or gross earnings, or any part thereof, its real estate and tangible personal property shall be assessed by a central State agency, as prescribed by law.