No person, firm or corporation shall allow lamp posts, telegraph poles, telephone poles or other structures projecting above the surface of streets or sidewalks to remain there for a period of more than thirty (30) days after the time when such posts, poles or other structures cease to be used for the purpose for which they were authorized and permitted. However, existing posts, poles and other structures that may be projecting above the surface of streets or sidewalks after May 14, 1951, shall not be required to be removed, unless the Director of Public Service orders them to be removed, in which case they shall be removed within ninety (90) days after the date of the order.