The use and bulk regulations applicable to a receiving site shall be modified as follows:

(a)        C6-4 Districts

Within Area A2 on the maps in the Appendix to this Chapter, the use and bulk regulations of the underlying C6-4 District shall not apply. In lieu thereof, the use and bulk regulations of an M1-5 District shall apply.

Within Areas B2 and B3, the use and bulk regulations of the underlying C6-4X District shall not apply. In lieu thereof, the use and bulk regulations of an M2-3 District shall apply.

(b)        C6-3 and M1-5 Districts

The use and bulk regulations of the underlying C6-3 and M1-5 Districts shall not apply. In lieu thereof, the use and bulk regulations of an M2-4 District shall apply.

However, on a receiving site, for any development, enlargement or conversion that is the subject of a special permit granted by the City Planning Commission pursuant to Section 89-21 (Transfer of Floor Area From Hudson River Park), the use and bulk regulations of the underlying C6-3, C6-4 or M1-5 District shall only apply to such approved development, enlargement or conversion.