I am bumping/updating this thread, based on my experience today.

There are no accessible NEXUS machines in the trans-border area. None.

With checked bags, I was escorted into a tiny room and asked to wait 15 minutes while my luggage was identified and brought up on a screen (a k a positive baggage identification). (In YYZ, this process takes 2 minutes and is automated).

I have no idea why the trans-border area is so slow, but you will definitely need extra time to navigate through this.