This excerpt taken from the PCG 10-K filed Feb 18, 2005.
9.2. Management of Emergencies by Participating TOs.
9.2.1 ISO Orders. In the event of a System Emergency, the Participating TOs shall comply with all directions from the ISO regarding the management and alleviation of the System Emergency unless such compliance would impair the health or safety of personnel or the general public.
9.2.2 Communication. During a System Emergency, the ISO and Participating TOs shall communicate through their respective control centers, in accordance with the Operating Procedures.