Bit late to this thread but I've been digging through my notes from Tuesday night.
I'm based in Suffolk so obviously wasn't there myself, but I do track international sighting reports fairly closely. A few things I'd want to know before getting too excited about this one:
What was the flight path doing? Phoenix sits under some busy corridors and the TR-3B crowd tend to jump on anything triangular without ruling out conventional traffic first. Were the lights static or pulsing? Moving in formation or as a single rigid unit?
I run a Yukon NV setup for my own fieldwork and the number of times I've nearly logged something dramatic only to realise it's military hardware or even a weird atmospheric reflection is... humbling. Keeps me honest.
The 11pm timing is interesting though. That's outside typical commercial peak hours for that area, isn't it? And triangular craft reports over the American Southwest do have a fairly consistent pattern going back decades - the '97 Phoenix Lights being the obvious benchmark.
Can you describe the altitude estimate? And was there any audible component, or completely silent? Silent triangular craft are the detail that tends to separate the genuinely odd reports from the mundane ones in my experience.
Not dismissing it - just want to understand what we're actually dealing with before drawing conclusions.