I'm pretty sure there is no pre clearance anywhere outside of Canada
Could be things changed, I remember when porter had an offer for slots at DCA and LGA but was not able to get them, because YTZ did not have a preclearance facility, so they had to go to EWR and IAD where customs can be done on arrival.
Could it be that it's different, ex EWR vs ex YTZ. Do they have customs in YTZ or do you clear when you land in EWR?