CTA power control

Hello, I would like to know what CTA Power Control is? I have heard them come up on various CTA rail Channels, is this who is in charge of cutting power to the third rail? Also with incidents involving CFD, I have noticed that the battalion chief often requests a secondary hold on the power, is this an additional safety measure? The fire alarm office used to call the CTA on 470.9875, but this has not been the case recently why is that? Thank you

I'm assuming a different dispatcher at CTA control that has the capability to turn the power to third rails on and off. Secondary hold is additional power grid in each direction, and they use CTA Fire frequency now..it's listed.