This is still accurate as of the end of 2016 and [MENTION=193352]paule123[/MENTION] 's experience last month is the same. You will check in with UA, after the UA desk but before security you will scan your boarding pass at a tablet and place any checked baggage you have on the belt. This will take weigh/take a photo of your bag automatically and dump it into a chute to enter the checked baggage system. You then go to the security line (where there is a CATSA trusted traveler line) and you generally require a GE/NEXUS card for access to the line - although there are limited other experiences (discontinued CBP sticker that they no longer apply/printout of GOES/new TTP website sufficing) reported in the wikipost and thread posts here ( Is a Global Entry card required???).

Once you're through security, at least at YUL, there's nothing preventing you from walking over to the GE kiosks - so if you were denied access to the TTP lane for CATSA screening, you can still walk over to the GE kiosks in the customs area and use them (assuming you're enrolled in GE or NEXUS/a foreign program that has reciprocity with GE and you're enrolled for that). The TTP lane will dump you on the right (GE kiosk side of the hall) and the regular/non TTP priority lanes will dump you on the left. You just walk around the back of the customs halls to the GE kiosks and use them. Once you use them, you wait in line to speak with an officer (who will generally want passport/boarding pass/GE receipt and to ask a couple questions).

Once you're done in the customs area you're dumped into the gift shop, and once you're through the gift shop, you're in the transborder sterile area.