Just popping my head in. The positive about digital emission is where a analog signal will "picket Fence" or fade out at the edge of the coverage area, Digital will be clear HOWEVER, when you hit the end of the coverage area it drops off like a rock, visually, analog looks like a wave and digital looks like a block. When its gone its gone. Anyone with a cell phone that has been dropped can attest to it.
The Fire service and the IAFF have done studies and until every skyscrapper in NYC is fitted with bi-directional amplifiers (CODE CHANGE) I seriously doubt FDNY goes 100%digital. It could happen, Vegas changed the Building code to require them so communications in hi rise hotels would be approved. Good luck getting retro code change, Clark county had to kill 84 people to get it done.
And yes the vocoders are better, but that is a simplistic answer to a complicated issue, Steel re-enforced construction, coverage gaps, below grade operations, RF interference and a host of other issues drive techs crazy. Food for thought: How extensive is your cell phone coverage, and how often are you getting dropped during a call? Bet their coverage is better than the cities...
Digital is the future not because of jee-wiz stuff but the demand for spectrum is high especially in NYC, with 5G coming the demand for features for just Public safety is mind blowing. some very interesting times coming, with some very complicated problems.