I was able to go through One Stop Security at YYZ.
You clear CBSA by international connections, and then instead of turning left you go down a flight of stairs.
If you look closely beyond the glass, you can see a Canadian Flag with the word 'Gates'. That sign is located after immigration.
You then go down the flight of stairs and then end up on this bus that will bring you to the D gates.
Can we merge all the OSS forums as this is confusing having 3 separate ones? Also, what is CATSA policy on those who land at their destinations from OSS airports and do not have any checked bags. Can they go through OSS, then through Domestic Baggage Claim?