Er, really? Usually it's the other way around. i.e. when flying from country A to country C via country B, in country B's airport you just go through a cursory security check but no immigration or customs formalities.
Yes, indeed. US/Europe to -> rest of world (except US) involves no security when transiting Canada.
Domestic connections do require security, connections to US generally require preclearance security. Connections from most other countries also go through security.
The odd thing is that they don't separate arrivals: so you'll mingle with worldwide arrivals, go through transfer immigration with everyone else, and finally you show your boarding pass and get routed either to the departure gates, or to security, based on your boarding pass.
Domestic connections do require security, connections to US generally require preclearance security. Connections from most other countries also go through security.
The odd thing is that they don't separate arrivals: so you'll mingle with worldwide arrivals, go through transfer immigration with everyone else, and finally you show your boarding pass and get routed either to the departure gates, or to security, based on your boarding pass.