The Counties of Fluvanna, Greene, Louisa, and Nelson may join the Authority, and the Authority shall embrace all or such portions as the governing body of each county desires to have covered. Additionally, private nonprofit tourist-driven agencies, higher education facilities of the Charlottesville-Albemarle area, and public transportation agencies serving such counties may join the Authority. The governing body of any county, agency, institution, or facility wishing to join the Authority and the governing bodies of the localities, agencies, institutions, and facilities then members of the Authority shall by concurrent resolution or ordinance or by agreement provide for the joinder of such county, agency, institution, or facility.