Unless you say you fly YYZ-HKG-YYZ as frequent as once per month or more, there is no guranteed the routing is the same as you described (polar outbound, normal route TPAC inbound, and you also didn't say which direct polar route goes, as it could be east or west)

Other than YYZ-HKG, there are also ORD-HKG (pay attention to my screename) and EWR-HKG.

In general, YYZ-HKG and ORD-HKG go west via polar route was to avoid in the likelyhood of strong jetstream that travel west to east. However, for the return flight HKG-ORD and HKG-YYZ, it will fly via TPAC as close to be the jetstream to gain speed, especially if you are watching the maps constantly, there are times I had seen the plane speed was as fast as 1300 km/h ! However, when the west to east jetstream is weak, I had flown ORD-HKG not polar but just via TPAC into Alaska, just north of Bering Sea.

EWR-HKG is different as usually no matter outbound or inbound are both polar, but many times they go in different action, like EWR-HKG could be flying east thru Greenland, North of England, then into or north of Russia, and the return HKG-EWR would be mainland China, Russia, North Pole, Alberta, then north of Lake Superior.

When they detect they are solar storms, it would also avoid Polar routes, which you should have heard that from the news too.