Again, you said "ALL carriers responded". Does not one carrier make that claim as wrong as two or three? If you wanted to say TMo has had a big impact on Sprint, and to lesser extent AT&T, then your contention would have been much more accurate.
And there's no proof VZW responding to an AT&T move is an indirect response to TMo. AT&T also does plenty of their own moves to compete with VZW that have nothing to do with TMo. Data prices (or at least bandwidth) are and were going to come down, just as it did with cell minutes, regardless of what TMo was doing.
VZW has never targeted the value/bargain hunter, so TMo going after the bottom feeders has very little, if any, influence on VZW.