No - by definition, his "unit" was the 27th A.A. Regt (a regiment or a battalion is considered a "unit").
His "sub-unit" was the 42nd H/A.A. Bty - probably the 140 guys in the photo (an artillery regiment is comprised of batteries, whereas an armoured regiment is comprised of squadrons, and a battalion is comprised of companies).
His "corps" was the Royal Canadian Artillery (not to be confused with a size of formation called a "Corps" - other corps are the armoured corps, the infantry, etc.).
P.S. (courtesy of Mike O'Leary, here's the link for the Archives:
... for requesting service records from the National Archives; http://www.collectionscanada.ca/02/020203/02020302_e.html