when they heard another aircraft east of Lismore at 5000’
They said they didn't hear it. Pack of cards falls down now. It can only be alerted see and avoid if you are alerted in the first place.
I would expect them
(the Jab)
to have made a radio call referencing BNA
The Jab obviously did not consider himself in BNA traffic mix, as he broadcast to LIS traffic. He didn't hear either of the A320 calls. See comments above
Would a Class D tower have prevented this? It wasn't in the BNA circuit. It was IFR-VFR crossing traffic 12 miles out. How big do you want the control zone? If there was overlaying Class E, does that not just add to the frequency conglomeration in that area. What freq are LIS and EVD meant to be on? The only thing that might have happened is the Jab may have avoided the CTA (thus the conflict) , which then brings the howls from the usual suspects of GA being hounded out of airspace.