Whenever a zoning lot existing on December 15, 1961, or on any applicable subsequent amendment thereto, is divided by a boundary between:

(a)        two Residence Districts limited to single- or single- and two-family residences; or

(b)        two Commercial Districts or two Manufacturing Districts in which the same uses are permitted but different bulk regulations apply;

the bulk regulations applicable to the district in which more than 50 percent of the lot area of the zoning lot is located may apply to the entire zoning lot, provided that the greatest distance from the mapped district boundary to any lot line of such zoning lot in the district in which less than 50 percent of its area is located does not exceed 25 feet. Such distance shall be measured perpendicular to the mapped district boundary.

Whenever the bulk regulations are so applied, the district boundary may be assumed to be relocated accordingly, and the off-street parking and loading and all other regulations applying to such expanded district shall apply to the entire zoning lot.

Except as specifically provided by the provisions of a Special Purpose District, the provisions of this Section shall apply to zoning lots that are divided by a Special Purpose District boundary line.