Section 15. (A.) Upon adoption by the registered voters of any county, except Barnstable county of any optional form of government set forth in this chapter, the county shall thereafter be governed by the plan adopted, by the provisions of this chapter applicable to all optional plans and by all general laws, subject to provisions of this chapter.

(B.) For the purposes of this chapter, a ''general law'' shall be deemed to be such a law or part thereof, heretofore or hereafter enacted, that:

(i) is not inconsistent with this chapter; and (ii) is by its terms applicable to or available to all counties, or, (iii) is applicable to all counties or to any category or class of counties and deals with one or more of the following subjects: the administration of the judicial system, education, elections, health, county public authorities, taxation, finance and welfare.

(C.) Except as it relates to judicial or penal administration, or the administration of the registry of deeds nothing in this chapter shall be construed to prevent counties from abolishing or consolidating agencies the existence of which has heretofore been mandated by general law provided that if such abolition or consolidation shall alter the obligation of the county to continue services theretofore rendered by such abolished or consolidated agency, said alteration must be approved by the general court prior to taking effect.

(D.) The intent of this chapter is to enable a county that has adopted a charter pursuant to this chapter to cause any duty that has been mandated to it by the General Laws to be performed in the most efficient and expeditious manner, and, absent a clear legislative declaration to the contrary, without regard to organizational structural, or personnel provisions contained in prior general law, and further, the intent of this chapter is to encourage a review of the functions which a county provides.