Whilst not stifling your debate and I am sure you guys know this, but some onlookers may get confused; please be in no doubt the aircraft was not in distress.
Reading from a Statement issued by Cathay Pacific, it would seem the Canadian Authorities (Vancouver Airport) received 2 bomb threats relating to an outbound flight (CX838), Vancouver to HK. The flight that was escorted was the inbound flight (CX839) being the same A340 that would later return as CX838.
Reading between the lines neither the airline nor the crew initiated this action.
Ultra-ultra cautious reaction by the Canadian Authorities I would suggest; good training value perhaps???