The A340-600s CAN fly HKG-YYZ-HKG if CX decides to use the Polar Route. The route was originally intended for the HKG-JFK nonstop. JFK is further than YYZ from HKG. But the Purser on CX said yesterday that there were 'concerns' from CX cabin crew about 'radiation' on those flights. So maybe that's why they haven't started the flights?