I've done those bench presses before we also have that same cambered bar. The bands create of ton of instability in the bench press, I would be a little apprehensive to try the same with anything heavy on squats. I do not think it would be anywhere close to an equivalent, but it certainly could make for some interesting assistance work.
I've seen someone on youtube hand a second barbell from a set of chains off the top barbell, that seems like it would be the closest to replicating a cambered bar movement. I think the video was posted here of a guy doing good mornings with that setup.