No, not much concern if everyone is doing their job correctly! It happens to be that many flights pass over Pearson because it is part of the flight-plan. The aircraft intercept the YYZ VOR or VHF Omni directional range, like a radio navigation system and sets the aircraft on a different airway or continue on the same on. When we passed over the Pearson VOR, the aircraft banked to the left and onto a different Airway. All done automatically by GPS.