The regional planning commission of any region, or the county planning commission of any county, shall, after making the regional or county plan as provided by section 713.23 of the Revised Code, certify a copy thereof to the planning commission of each municipal corporation of the region or county, the board of county commissioners and county or regional planning commission of each county or region or part thereof included in the plan. In the event of the subsequent creation of a planning commission for any municipal corporation within a county having a county planning commission, or for any municipal corporation subsequently incorporated within the area of a region having a regional planning commission, a copy of the county or regional plan shall be immediately certified to such planning commission.