I successfully signed up for the eGate yesterday arriving into T1 with CX. Due to the weather disruptions on my flight schedule, I ended up trying to enroll on a day before my scheduled appt. No problems, they found me in the system and had me signed up. Didn't even ask to see my NEXUS card.
US passport worked the first time I inserted into the eGate reader.. Didn't find it hard to read at all.