(a) Tangible personal property which is moving in interstate commerce through or over the territory of the State of West Virginia, or which was consigned from a point of origin outside the state to a warehouse, public or private, within the state for storage in transit to a final destination outside the state, whether specified when transportation begins or afterward, but in any case specified timely for exempt status determination purposes, shall not be deemed to have acquired a tax situs in West Virginia for purposes of ad valorem taxation and shall be exempt from such taxation, except as otherwise provided herein.
(b) Such property shall not be deprived of such exemption because while in the warehouse the personal property is assembled, bound, joined, processed, disassembled, divided, cut, broken in bulk, relabeled, or repackaged for delivery out of state, unless such activity results in a new or different product, article, substance or commodity, or one of different utility.
(c) Personal property of inventories of natural resources shall not be exempt from ad valorem taxation unless required by paramount federal law.
(d) The exemption allowed herein shall be phased in over a period of five consecutive assessment years, at the rate of one fifth of the assessed value of the property per assessment year, beginning July 1, 1987.