Do a little more research. The only data PASSUR receives from an ASR system is 1030 MHZ interrogation data (transponder data). If the target isn't transmitting an IFF code, it won't show up when it is interrogated by an ASR system and there is nothing to be sent to the PASSUR system.
"the FAA ATC tapes may not have designated the bogey as the AA flight."
Where have you seen those?
"TCAS is NOT implemented on ALL commercial aircraft. ONLY those with FAA oversight."
Again, you need to do more research. TCAS is currently required on all commercial aircraft (part 121) and all cargo aircraft with a max takeoff weight of more than 33,000. The same is true internationally.
"Also, it is entirely possible that this was another aircraft that wandered into the airspace with it's IFF turned off."
Then it would have been seen by ATC radars used to track raw returns (not transponder data) and would have been reported to AA 612.
"I can turn IFF off on my plane anytime I want."
Yeah. And do it in Class A airspace (where this event occurred) and then you really will see fireworks. I've been scrambled for similar events.
"Did the AA pilot report a TCAS warning?"
No, which is really all the proof you need that what shows up on the PASSUR display is a ghost image. If it were real, AA 612 would have been climbing and diving all over the sky to avoid a collision.
If as you claim the entire system only works on IFF data how did ASR assign the same ID to two different IFF responses and then feed it to PASSUR? One system decided to give the unknown an ID OR it responded the same ID as the AA flight. Either way your argument doesn't work.
You don't think that a cargo plane of under 33,000 pounds could cause this image?
Yes PASSUR uses the 1030 data. So then that means either the FAA assigned the image the same data as the AA flight or PASSUR took an unknown and assigned data to it. Either means something is wrong with the entire system.