6After that subsection there shall be inserted the following subsection—
“(1A)Notwithstanding the provisions of paragraph (b) of subsection (1) above, in the case of a building or structure the site of which is or has been in an enterprise zone, any expenditure which a person is deemed to have incurred by virtue of that paragraph shall be treated for the purpose only of determining entitlement to allowances as not incurred, and not incurred under a contract entered into, at a time when the site of the building or structure is in an enterprise zone.”