In case a public utility changes its name, a tariff supplement shall be filed setting forth that fact. Unless otherwise permitted by the Commission, when one public utility is acquired by or absorbed with another public utility, the predecessor shall unite with the survivor in common supplements to existing tariffs, the predecessor withdrawing and the survivor accepting and establishing such existing tariffs. The common supplements shall be executed jointly by the officers of both predecessor and survivor utilities, and numbered as supplements. New tariffs or schedules shall be numbered in series as of the surviving utility. Similar provisions shall apply to receivership of public utilities.
52 Pa. Code § 53.5