I was in NYC a while back and walked past fox news around 10pm heading back to the hotel. The studio is windowed to the street and not a single person was in there. Total darkness.
In fairness, they have more than one studio. The studios with windows onto the street -- at Fox, CNN, NBC and ABC -- are generally used only for the morning shows when there's a large and relatively wholesome crowd gathered at the window. They don't want the cameras and lights pointed out there when the drunks and hookers show up.