CRA acknowledges that options on Canadian real estate company shares are exempt under the Canada-US Convention

The capital gains exemption in the Canada-US Income Tax Convention for qualifying US residents does not apply to alienations of shares of Canadian real estate (or resource) companies.  The Canada Revenue Agency has acknowledged that this exclusion does not apply to capital gains from alienations of options on such shares - nor are there any rumblings of the general anti-avoidance rule potentially applying where a US resident relies on this exemption (e.g., the US resident structures its investment in a Canadian real estate company as a long-term option on the company's shares with a low strike price).

Neal Armstrong.  Summary of 22 June 2012 T.I. 2011-0416521E5 under Treaties - Art. 13.