Having flown for both the NBC affiliate and a sheriff department in the San Francisco Bay area I can probably help you out here.
In the SF area there is no written policy, but there are "air to air" frequencies that we all monitor. All the professional pilots also know each other and bar-b-que occasionally and work things out. Unless there is a TFR in place, the news helicopters will be talking directly to the LE pilot over the incident. There have been times when the news guys help out the police pilots with information also.
Also the news pilots will be talking to each other while over incidents and working out our own separation, and altitudes. I remember covering many stories where we would alternate who went lower, normally determined by who was going "live" at the time or who had what camera capabilities.
We all work in the same airspace and all of us are just trying to earn a living. Certainly it has been my experience that we work together for the common goal of going home that night, bt I do know there are some jurisdictions that do not have good working relationships.