I'm not entirely sure that I understand the question but my understanding of TCAS II is that it is an intercommunication system that provides 'Traffic Advisories' (TA) and ultimately 'Resolution Advisories' (RA) between 2 aircraft that are Mode C or S equipped and thus using Mode C or S. However, should there be a Mode A transponder around then the TCAS equipped aircraft will still give a TA but not give an RA. Frequently (more than once a month) I get a TA going into LGW from aircraft much lower than us over the South of England and even during the climb out from aircraft that are operating from fields below the LGW TMA. Hence SID's usually say "to be 3000' by DET 32d, 4000' by DET43d" for example.
The TCAS II RA's give instructions to "Climb", "Descend", "Increase Climb/Descend", "Monitor Vertical Speed" and "Climb Crossing Climb". Not doubt there will be more but I did my ATPL's some years ago and as they say S.I.S.O.
Do as you're told and you can't go too far wrong. I think that I'm right in saying that this is the only time that a pilot can deviate from an assigned FL without the command of an ATCO.
It does not give lateral commands, and my understand of that is that this was for TCAS III which has been inched to the back burner.
As for ATC not knowing about the impending TCAS RA then I beg to differ. A former Capt. at my airline had a TCAS RA at his previous airline when another a/c was cleared climbing through his level and when he got the subsequent AAIB report he was surprised just how many 'bells and whistles' the ATCO's have at their disposal. Apparently the warning lights/sirens were going off well before he got his TCAS RA. Chris, I hope that I'm not misquoting you and we all hope you're doing well now.
On a completely different subject, hats off to you ATCO's. You're job sounds so stressful at times and yet you still manage to remain so chipper!
Oooh! And as for the Radio Failure. Sqwawk 7600 and follow the flight plan and STAR to the letter! Then let the finest ATC facility in the world clear the airspace for you. You are after all an a/c in distress.