Actual upgrades as a non-AA OW elite. Unless the route is a very oddball route where there isnt a lot of upgrade traffic (e.g., PHX-TIJ) I would say the chances are minimal. You have to have a flight where every AA FF who is eligible for an upgrade has either upgraded or purposely declined the upgrade (family that doesn't want to split up). Best chance of that happening is, as noted above, CR700 or E175 flights where the upgrade queue is zero.

I have seen them, but almost never on mainline.