Originally Posted by WR Cage

If the OP is flying to China from YYZ T3 that means they are departing either MU or HU.

To answer the OP question, they are arriving T1 Transborder and Departing T3 International. They will not be able to utilize the quick USA to International connections process because they have to transfer terminals.

I will go out on a limb and assume for purposes of discussion the OP is travelling on split tickets. In this instance the OP will have to pick up their bags on both connections at YYZ. Further the OP will not be able to checkin until approximately 3-4 hours prior departure. This will limit the amount of time the OP has to enjoy the lounges.