I have picked up from private jet at YYZ but it was from a transborder flight. There is a separate private jet terminal that is infield at YYZ. Not sure who the service provider is. Once you exit the terminal, you have direct access to exit the airport so I assume immigration is done at the private terminal. To get to this terminal, you can use Brittania Rd from Dixie Rd or from Renforth Rd to Convair Dr, pass the GTAA control tower and on to silver dart drive.