(2)Notwithstanding anything contained in this Chapter, lands and buildings, which are the properties of the union, shall be exempt from the property tax:Provided that nothing in this sub-section, shall prevent the Municipality from levying on such lands and buildings a tax to which immediately before the commencement of this Act, they were treated as liable:Provided further that the Municipality may levy a service charge on such buildings on the basis of such annual value and at such rates, as may be determined by the Central Government.