Droopy makes some very good points! But surely,the real issue must be coverage, rather than whether the unit is purely a Police function or carries a dual role.
We can argue for hours as to whether a criticaly injured patient stands a better chance in a pure & specialised ambulance aircraft or a "Dual hatted" one. Or whether a specialist Police aircraft is more efficient than a part ambulance machine. Its time to task and whether there is still a job to do when you finally get there, is what ultimately is the decider in "Good job or failed"
It comes back to that old question of the range of efficiency being about 15-20 minutes.
In the long run a National Emergency Services air wing would be the most efficient. That would permit the proper placing of a mix of aircraft where they could provide the best service to all of the emergency services and ultimately to the people of this country. The national unit would have its own spare aircraft to fill in for downtime, Pool of pilots and its own maintenance regime.
If the National Crime squad, NCIS etc can do it why not emergency services
aviation?