38Where an interest of the Postmaster General in land vests in the Post Office by virtue of section 16 of this Act and, at a time when the interest was vested in the Postmaster General, the land fell within any of such descriptions of land as, for the purposes of section 84 of the [1967 c. 1.] Land Commission Act 1967, were agreed between him and the Treasury as being at that time descriptions of land which, in relation to functions of his, corresponded as nearly as may be to the descriptions of land which were operational land in relation to statutory undertakers, then, for the purposes of section 58 of that Act, the land shall be treated as if, at that time, it had been operational land of the Post Office.