(1) Where an amount has been paid to or recovered by the mortgagee under a mortgage in respect of a liability that, upon the making of a claim by the mortgagee, is, by section 68, taken to have been discharged as from the time of acquisition of a mortgage interest under the mortgage:
(a) the mortgagee is liable to repay that amount to the person who paid it; and
(b) the Commonwealth may deduct from the compensation payable to the mortgagee and pay to the person who paid that amount so much of that amount as has not been so repaid.
(2) A payment made by the Commonwealth under paragraph (1)(b) shall be deemed to have been made in discharge of the obligation of the mortgagee under paragraph (1)(a).