This Part applies to all base buildings and all tenant spaces for which a green building credit is being sought by the taxpayer(s), whether the green building credit being sought includes (or consists of) a green base building credit component, green tenant space credit component or green whole-building credit component, as those terms are defined in section 19 of the Tax Law. This Part takes effect immediately except that with respect to allowable costs paid or incurred by the taxpayer the effective date is June 1, 1999.