For all purposes of this part relating to Section 218(c) of the Social Security Act, employees in any class or classes of positions covered by a retirement system excluded from the agreement pursuant to paragraph (3) or (5) of Section 218(c) of the Social Security Act at the time it is made applicable to such retirement system and to which the agreement does not already apply shall constitute a separate retirement system coverage group.

For the purposes of the referendum among eligible retirement system employees in such retirement system coverage group as required by Article 2 of Chapter 2 of this part and Section 218(d) of the Social Security Act, each such class shall constitute a separate retirement system.