I flew in Suffield (I'm a Canuck) back in the early 80s. If I remember correctly the Army call sign was used by Beavers and Gazelles just to avoid confusion with Canadian ATC on VHF. (instead of using unit / AAC call signs).
Within the confines of Suffield they used their own call signs on UHF and VHF/FM.
As for the size of Suffield it certainly is all perspective. I was from 427 Sqn in Petawawa Ontario Canada and to us, Suffield and Wainwright to the north were both frustratingly small. They were both only around 100 sq K. We were used to our 300 sq K ranges and our 650 sq K low flying area. I remember some lads from the US Army 101st coming up and getting royally lost. They were amazed that the area had no towns and certainly no VORs which they used all the time around Fort Rucker.
But back to the Beaver, great machine and we loved seeing the AAC birds drone around Suffield. It was always fun to hang out with those guys and visit to learn from each other.