Mark,
I do not know enough about Hamilton or Toronto to hazard a guess as to how intact they are, but I am sure Ian, Jeff or Robert will know.
As far as Ross' work in Winnipeg, quite a bit remains, but sadly has been altered. All three courses existed prior to Ross' involvement, and his work consisted of redesigning 9 holes at St. Charles and 18 holes at Pine Ridge, and redesigning 9 and expanding Elmhurst to 18 holes. Bill Newcomb re-worked St. Charles and Elmhurst in the 1990's, and Les Furber altered 4 greens at Pine Ridge during the same decade, and it remains the most preserved of Ross' work. Both Elmhurst and St. Charles have engaged the help of architects who have strong records of restoration, in Ron Prichard and Mike DeVries respectively. I would say Elmhurst has about 12/18 intact holes, and 14/18 original greens, while St. Charles has roughly 6/9 holes intact, and 4/9 original greens.
TK