According to the website of Les amis de la montagne, the communications tower is on the highest of the summits of the Mont Royal.
http://www.lemontroyal.qc.ca/carte/e...Summit-41.html
I had a great time last February on one of the snowshoe hikes that they organize. And I've spent a few hours wandering around in autumnal weather. I can't wait to get back there in warm weather later this summer.