TCAS installations include inhibitions of the various upwards RA's based on performance. A number of parameters can be considered, most obviously Altitude and Configuration, but other things can be considered, e.g. is the ice protection on to an extent that implies the aircraft is in Icing?
So there may be multiple envelopes for the enabling / inhibition of Increase climb and climb RAs.
Glueball, respectfully I must disagree. There is a lot of type dependancy in there. Cruising at ceiling isn't the worst case anyway, but rather near top of climb is. When TCAS was Mandated I was flying ATRs at the time, and the idea that we would be able to always zoom climb 500 feet is pretty optomistic. (A typical climb in icing conditions would be at or near to minimum clean speed, with a ROC of maybe 300 fpm as MAUW and a climb power pretty much equal to MCT. Putting the Props to Max would get us a bit more, but 1500 fpm... no way)
Needless to say, in that aircraft a strengthened climb RA was inhibited pretty much always IIRC, and a normal climb RA most of the time, but even the performance envelopes specified were pretty optomistic.
Which is why everyone should know that protecting the flight envelope is more important than following the RA, and what they should do if they can't achieve the RA, which is to get as close as possible with a cardinal rule of not manouvering opposite.
pb