This part shall not be construed as repealing or impairing any provision of any private act relating to the approval or regulation by the municipal authorities of the cities therein specified of the subdivision of land or the filing of plans, plots or replots of land lying within the distance therein specified beyond the corporate limits of such cities, or of any private act relating to the jurisdiction of any county planning commission of the county therein specified.
T.C.A. § 13-3-409