I drove my car for several weeks around Ottawa with no front plates and no one noticed. Then again around here we have plenty of cars from Quebec so it doesn't stand out or anything. Mind you I did drive to Toronto a couple of times.
Being in Ottawa so close to Quebec, the cops aren't "surprised" to see cars without front plates like they are where I am. I rarely see a car without a front plate, and if I do, it is quite noticable, and I'll usually try to catch a glimpse of the back plate to see where they're from (mostly Quebec).