OSS, One Stop Security Initiative
At YYZ T1, they've put up a new CATSA screening area at the area for connections to "E" gates. That's the little area with a couple of border officers you see when arriving from outside Canada and departing on an international (non-USA) flight at T1. In the past you'd see immigration, then head to your gate. Now it seems you'll also see CATSA before heading to your connecting flight, unless arriving from the USA or the EU.