Chugalug2:
Canada did have OTU,s as there was a need for operational squadrons to counter threats on both coasts. On the east coast, the Nazi U boats wreaked havoc, particularly in the Gulf of St Lawrence, and off the eastern seaboard. In fact ships were torpedoed just leaving Halifax harbour. The public also had a perceived notion the Germans has a secret long range bomber, (which never existed) and defenses were formed according.
The west coast was under attack by Japanese forces to a small but very worrying degree. Their submarines also patrolled the area, and in fact did shell a lighthouse at Estevan Point, Vancouver Island. While the damage incurred, was very minor, the uproar, like the Doolittle raid on Tokyo, was enormous.
The Japanese also had a very crude form of long range weapons, which turned out to be very ineffective but set the populace on edge. Basically incendiary bombs were fastened to balloons, launched from Japan, and after a set time drifting eastward, the bombs released. Thousands were launched, but few reached Canada, and even fewer anywhere near a populated region.
All of these did require the formation of some fighters squadrons, mostly using Hurricanes, and search and rescue and anti submarine operations, using a variety of aircraft.