Try looking under "Native Air Ambulance" and their ownership group - "Air Methods, Inc". Banner does not run its own air ambulance department. Air Methods is the ownership group of a large number of air ambulances in the United States. Native Air is their DBA name for Arizona, California, Nevada, New Mexico, and Texas.
From the 8 pages of FCC files [both PW and IG services], I found one entry for Arizona:
WQXG336
Locations: ON TOP OF GREENS PEAK; PINETOP, AZ APACHE County and MT. ORD; PAYSON, AZ GILA County
Frequencies:
451.35000000
451.96250000
451.96250000
456.40000000
463.78750000
463.78750000
468.78750000
I checked only active licenses, not cancelled, expired, etc.
There is one entry for Christmas Tree Pass in Laughlin, Nevada.
I did not explore the possible links between Banner Health and Air Methods. Memos of Understanding, contracts, etc. can take a lot of time to unearth, research, and determine uses.