(1) An authority incorporated under Act No. 55 of the Public Acts of 1963, being section 124.351 to 124.359 of the Michigan Compiled Laws, or an authority having a population of less than 1,000,000 incorporated under the metropolitan transportation authorities act of 1967, Act No. 204 of the Public Acts of 1967, being section 124.401 to 124.425 of the Michigan Compiled Laws, may form a public authority under this act. Political subdivisions which are members of an authority described in this subsection which form a public authority shall be members of the public authority.

  (2) Formation of a public authority pursuant to subsection (1) may be accomplished by adoption of articles of incorporation by resolution adopted by a majority of the members serving on the governing body of the authority incorporated under Act No. 55 of the Public Acts of 1963 or Act No. 204 of the Public Acts of 1967.

  (3) An authority created under an interlocal agreement pursuant to the urban cooperation act of 1967, Act No. 7 of the Public Acts of the Extra Session of 1967, being section 124.501 to 124.512 of the Michigan Compiled Laws, for the purpose of providing public transportation service may form a public authority under this act. Political subdivisions which have created an entity described in this subsection which form a public authority shall be members of the public authority.

  (4) Formation of a public authority pursuant to subsection (3) may be accomplished by adoption of articles of incorporation and by amendment of the interlocal agreement by resolution adopted by a majority of the governing body of each public entity which were parties to the interlocal agreement. In addition, if a separate legal or administrative entity was created under the interlocal agreement, a public authority may be formed pursuant to subsection (3) only with the approval of the entity empowered by the interlocal agreement to bring action in court against other entities, on behalf of the authority created under the interlocal agreement.