Behind the scenes
Two different lines of communication are in use when the copter is on the air. One from the ground to the copter, one from the copter to the ground. That configuration changes when the helicopter's transmitter is turned off.
The anchors, when on the air, are broadcast for all the world to see and hear from their transmitter on Lookout. That signal is simulcast on a company frequency, picked up by the copter and refered to as what is known in the industry as IFB. Interruptable Feed-Back. Interruptable meaning that a show producer or someone else behind-the-scenes can interrupt the simulcast and talk to the copter crew on that frequency. That's the line of communication from the ground to the copter. When it's time for the anchors to talk to the copter, all the copter crew is doing is listening to the same broadcast that everyone else hears.
The helicopter is constantly transmitting a microwave signal carrying audio and video back to the station. That is the line of communication from the copter to the ground. The reporter is using the same microphone that she uses on-air. At the proper time, the control room simply puts that microwave signal on TV.
So you've got the station talking to the copter via IFB, and the copter talking to the station on microwave. Which, for your monitoring purposes, means you'll only hear the station's side of the conversation. For example:
Producer on IFB: "Thirty seconds. copter."
Copter on microwave: "Copy. Thirty seconds."
Thirty seconds later: Anchor on TV and simulcast on IFB (but no-one in interrupting the simulcast signal) "...Let's get a birds-eye view from the copter. Jane, tell us what you see."
Copter on microwave with signal now on TV for the world to see: "Quite shocking Dick. It appears Boulder City Hall is collapsing under the sheer weight of the hubris and hipocracy contained within the heads of those inside. There is no hope for the structure, but crews are working desprately to enlarge the doorways so those with extremely large heads can escape before the building sinks to the center of the planet..."
(Hey- I can dream, can't I?)
Also, there is probably some time-based compensation built into the IFB signal because of delays in digital signal processing from the copter's transmitter to the station and then out to the transmitter on Lookout. Usually one or two seconds. (When that signal gets pumped through places like Comcast's or Direct TV's systems, there can be as much as a 18-second delay from image aquisition to your TV set.)
When the copter's transmitter is turned off, both station and copter switch to another company frequency and talk "normally." At that point, you'll of course hear both sides of the conversation. When it's time to go back on television, the microwave is powered up and the crew monitors the IFB frequency.