Wirelessly posted (BlackBerry8530/5.0.0.601 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)
CX does not serve YUL. If you combine two partners on a BA miles redemption, you will be charged the more expensive distance-based redemption rate (for example, 70,000 BA miles to fly YUL-JFK-HKG-SGN one way, or 100,000 miles roundtrip, using BA's oneworld award redemption table).
BA also imposes substantial fuel surcharges for redemptions to Asia from North America.