G-1 is probably the most active for spontaneous multi-agency incidents.
The H-deck interops are encrypted.
There is also the Ocean deck interops. I think these are mostly used for incidents and events in the fringes of the Phoenix metro area. Incidents and events are assigned the same as G-deck.
There is a pdf detailing the assignment of G/H/L/O-deck talkgroups. Go to this page, and there are links on the left detailing interoperability procedures.
Regional Wireless Cooperative
Phoenix PD Firebird can frequently be heard assisting DPS on their metro channels. Much more often than DPS' own Ranger helicopter.
John
Peoria