Every owner operating a licensed taxicab prior to the nineteenth day of December, 1951, shall be presumed, in the absence of any contrary evidence and finding of the council, to have established a prima facie evidence of public convenience and necessity for the licensing of the taxicab or taxicabs actually in operation, and the council, upon application received not later than fifteen days after the nineteenth day of December, 1951, shall grant a certificate of public convenience and necessity to such owner for the operation of taxicabs. Every owner obtaining a certificate as aforesaid shall be entitled to the number of taxicab permits held by such owner that were in force on the day prior to the nineteenth day of December, 1951. (Prior code § 6240.8)