Ok so in Chicago with the L system, a secondary hold is when CPD or CFD requests an additional hold on the power. This is to make sure that power is not restored unliterally, once CPD or CFD personal are clear then the secondary hold is released and power can be restored. A similar procedure exists in the suburbs that the L runs through. Also at the CTA control center there is someone who's sole job is handling the system wide power grid, this is known as "power control." I would imagine has something similar? Do NYPD and FDNY have something similar to what I mentioned above?