Sec. 203. (a) ADVISORY. After a metropolitan plan commission is established, it shall exercise exclusively the planning and zoning functions of the county and of the second class city, and the separate planning and zoning functions of the county plan commission and the city plan commission cease.
(b) AREA. After the planning department is established and the participating legislative bodies have adopted a zoning ordinance, the planning department shall exercise exclusively the planning and zoning functions of the county and of the participating municipalities, except as provided in section 901(i) of this chapter. Where other statutes confer planning and zoning authority on a participating municipality or a county, their plan commissions shall continue to exercise that authority until such time as the planning department is established and the participating legislative bodies adopt a zoning ordinance.