I'm sure there are holes in the system but several FB friends and others have said they've received a number of calls and visits while quarantining. In any case, we are doing as much as everyone else and the variation on the virus would arrive here in any case.
My brother in law flew from San Francisco to Toronto for Christmas. Did his quarantine at an Airbnb. He's heavily into tech (MSc from MIT in computer science) and took a long look at the app. He said that the quarantine app tracked his location through the phone (he didn't leave the condo for 15 days). No knocks but did get phonecalls. Everyone else I know has had knocks as far as I know.
I suspect that if it does track your phone and you were shown to have movement you would get a knock...