What does the OMB have to do with this?   It is the municipality of Oakville that has declared the Abbey as a heritage site, not the OMB.  

And RT is correct - there are many other sporting sites and golf courses that are better candidates for heritage sites than Glen Abbey.  The Niagara on the Lake golf course for one which is the oldest golf course in North America.  Hamilton G&CC and Toronto GC as well as they are early designs by H.S. Colt from over a century ago.  Or some of Stanley Thompson's best designs like St. George's.