Hi Ned,
Both the AANI and the PSNI helicopters use their respective TETRA systems to communicate with colleagues on the ground, this is not receivable by third party equipment.
The aircraft communicate with Air Traffic Control on the usual local frequencies as and when required near airports, they tend to operate below controlled altitudes elsewhere so contact will be minimal?
I am not aware of either carrying the marine band capability that a rescue helicopter would use to communicate with coastguard ground personnel or mountain rescue personnel so unsure if there is any opportunity there?