Listening to MedFlight can be very interesting this will hopefully help you understand the communications procedures for MedFlight here in Massachusetts. The first step in the communications is usually via pager to the pilot with incident info. The Initial radio communications between the "Boston" (Boston MedFlight) dispatcher and the MedFlight crew will be on 460.800 MHz with a Pl of 114.8. Initial communication to helicopter may include Landing Zone (LZ) coordinates, patient condition, LZ commander ID, frequency, etc

After receiving the call the helicopter will then switch to the local city/town fire frequency to get updated patient information and confirm the LZ location and give their ETA to the LZ. When the helicopter arrives at a scene of the incident, they will then make contact with the LZ Commander to assure the LZ is secure (clear of obstructions & hazards)  for landing. The Landing Zone(current list) is in most cases a pre-defined area at least 60' x 60' and is generally a parking lot or field and in some cases the LZ will be right on the roadway. 

When the helicopter leaves the scene and heads for a hospital, they will check in on 460.800 MHz and give an update to the "Boston"  MedFlight dispatcher (i.e.: clear of scene, en route to hospital, ETA, number of persons on board (POB) and amount of fuel on board.

The helicopter will then most probably switch to 463.075 (Boston C-Med)  and contacts the CMED operator. The CMED operator then assigns a MED channel (see list below) for the helicopter to talk to the receiving hospital . After the helicopter finishes reporting to the hospital, they go back to 463.075 to tell CMED that the MED channel is clear.

The helicopter will then go back to 460.800  to advise the “Boston” Med-Flight dispatcher that the helicopter is arriving at the hospital.

Listening to the input side of the C-Med channels (468MHz) and the input to Boston Med-Flight (465.800 MHz) will often get you details on the patient condition and other information. You do not necessarily need to be near the incident to hear these reports because they can be heard over long distances due to the elevation of the helicopter.

On the aviation band side of things - I suspect that a helicopter coming out of Bedford initially talks on 118.50 to Bedford Tower, and then switches to 124.40 to talk to Boston Approach in the 495 / 128 area. If the helicopter flies a patient into Boston which is usually the case, I suspect that they will switch to 124.725 Boston Skyways / Logan Tower inside the Rte 128 loop.

130.575 is a backup channel for Boston Med-Flight.

Out of area helicopters like LIFEFLIGHT out of UMass in Worcester, LIFEFLIGHT of Maine,  Life Star from Hartford, Ct. DHART from New Hampshire,  usually come up on the 460.800 MHz and talk to the Boston Med-Flight dispatcher when doing transports into Boston. The dispatcher will then gives the pilot a heads ups on other helicopter's in the area or en route to the various hospital helipads.

 
 

The C-Med Frequencies - Pl's vary with location