A special law for a single county, except a metropolitan county as defined in section 473.121, subdivision 4, and any other county containing a city of the first class, which authorizes the county to establish subordinate service districts or areas is hereby superseded. Any service being provided pursuant to the special law on or before the effective date of Laws 1982, chapter 507, sections 1 to 12 may continue to be provided pursuant to the special law.