Here are my preliminary findings:
The frequencies used for Tacs B and C have been repourposed. Therefore Tacs B and C have been deleted from service. Tacs A, D, and E have been redesignsted as Patrol tacticals and are available for use across any radio zone. Therefore any grids, as shown above in '320's post or on N2NOV's great webpage, linking particular Tacs to specific radio zones are no longer valid. In other words, any precinct units can use any of the three Patrol tacs now available to them at will.
It is unclear, at the moment, where the MetroTech Area security detail - a primary user of Tac B - went after the realignment. Further details will be forthcoming, as I am able to develop and confirm them.
Doc, you are correct. The tacs are low power point-to-point channels. It is quite likely that you won't hear anything on them, depending on where in the five boroughs you are and who may or may not be operating in your vicinity. I reiterate, though, my recommendation is, if space permits in your scanner, to program in all, now, 26 tactical channels. At the very minimum, space should be found for Tacs A, D, E, F, G, and H, as my observations are that they are the most widely utilized of all the tactical channels.