During continued substantial compliance with the terms of this article by the owner of any telephone exchange, the charge levied hereby shall be and continue to be in lieu of all concessions, charges, excise, franchise, license, privilege and permit fees, except special assessments and ad valorem taxes. It is not intended hereby to extinguish or abrogate any existing arrangement whereby the city is permitted to use underground conduit, duct space or pole contacts of the company for the fire alarm and/or police call systems of the city.
(`90 Code, § 5-21)