Ferris,
Vanman's point is key. You said 'it was FULLY UNDER CONTROL' sadly most ATC errors occur whilst the the aircraft is fully under radar control. I am not slagging purely, stating my opinion that we all screw up; even ATC guys. Most of the time though it is the pilots misunderstanding the controllers. We are fortunate in that we have 2 guys around to try to make certain that we trap the errors.
Anyone can point fingers and use Harry Hindsight to solve a problem that has already happened. (C'mon Seriph) I watch TCAS on a day to day basis as you watch the radar and the update rate is significantly higher on TCAS than on any search radar that I have seen in sweep mode. Short of getting a radar that has single target priority track on all the aircraft within its sweep; there will be a delay. (Bring on phased arrays!) We all look at a historic picture, the key is to recognise the picture offering the highest probability of reality.
All parties will react to the information that they consider the highest priority and that provides the latest information. For pilots that goes: Mk1 eyeball, other pilots Mk 1 eyeball, TCAS, ATC, PPRUNE.
For ATC mates (Have to admit my best mate is an ATCer, utoh) it will probably be secondary radar followed by primary coz the altitude recognition is better on secondary.
The info priority is moot, the bottom line is that ATC guys have the big picture and should see the disaster coming together earlier and that is their best time to intervene. The pilots see it all happen later and they will have less faith in the guys with the big picture as impact approaches. You are a very brave man if you think you really can solve the problem during the gravy strokes.
It is easy to start attributing blame but the chain was unbroken by all parties and the ATC mate, given good info from his sensors, had the longest time to solve the problem, followed by the pilots as the collision approached.
Ferris, you are absolutely right, mitigating the situation at or before the TA stage is preferable. Preferably at about 50 miles.
If ATC try to intervene at the TCAS RA stage they have either missed the opportunity to intervene earlier or have not had the chance. In most cases at this late stage they will only end up confusing the situation. (Ask any military Fighter Controller that has gone from a standard search radar to the ACMI, a GPS based real time information system.)
In the end game, the pilots are probably so cluedo and shocked, that the chances of you getting the message across in the last 20 secs are not high; therefore they will follow the most compelling (and most accurate) info be it visual or TCAS.
Getting my sanctimonious head on if everyone had done ther job perfectly, this accident would probably not have happened. Sadly, it was a clear day in 1923 when I last flew a perfect flight, a hop in the Sopwith Camel. More likely I just didn't spot the mistakes.
The best thing to come from this, from my point of view, is that I have been forced to re-assess my way of working. Hopefully, I will incorporate some of the good ideas into my working routine that other mates (pilots and ATC) have presented.
Ghost