There have been reports of travelers being blocked from accessing the Global Entry kiosks at preclearance facilities in Canada - I remember YUL and YYZ being mentioned? - for failure to show a Global Entry or Nexus card. This was not my experience about a year ago at YYZ, and I have never flown out of YUL on a preclearance flight.

You do need to present a Global Entry or Nexus card to enter the expedited security lanes in Canada, but my experience is that you have unimpeded access to the Global Entry kiosks after security, at least at YYZ and YVR.