FDNY-EMS Dispatch vs Tac?

When does NYC EMS use dispatch and tac? Usually a tac channel is used for units to communicate with each other in the field but the EMS Tac channels have a dispatch as well.

Don't bother listening to Tac channels, they are never used. EMS is dispatched over MDT and are giving the nearest intersection of the job and a vague assignment type to acknowledge over the air.

Each dispatch zone is assigned a tactical channel that is separate frequency for use as needed. However it is not practical and doesn't do anything for us. Now if the tactical channel was replaced by a simplex version of the dispatch, it would be helpful.

We are changing radios and layouts soon, haven't seen the EMS list but I heard these may get removed.