All electrical lines not exceeding 15,000 volts and all telephone and cablevision service lines, as well as other utility lines serving any new building or structure, including signs and billboards, requiring permanent electrical service shall be placed underground unless a waiver from such is approved by the Building and Engineering Departments. The provisions of this section shall not apply to existing buildings or additions to such buildings (unless said addition requires the utility service provider to upgrade the entire system from the transformer to the structure). Nothing in this section shall be deemed to apply to temporary service when defined as such by the utility provider.