digital, never mind encryption on a fire ground is a no-go all day long. There are studies about the topic. I don't think you'll see encryption for line companies. Maybe for chiefs and above at some point but I wouldn't worry about it.
The APX line offers much more capabilities that the old XTS line doesn't. I would think the current zones will stay the same. Especially for line companies. The chiefs and higher ups will probably have more access to more zones and channels.
I got a look at one of the new APX radios...They have 45 zones in them and many digital and encrypted channels. Lots of interop channels.
The main zone is mostly the same as the old radios and the main fireground is still low power with no PL LOL, They did get all the bells and whistles but fell way short on programming them correctly, Having used the APX for a few years now, they did not program them correctly at all.
Its a shame as the APX is a super radio when it comes to audio and they didn't use the settings at all
As for Digital and encryption on the fire ground...1999 called and wants its incorrect information back LMAO..Digital is far superior to analog on the fire ground and the APX is a rock star at it, but since FDNY tested an old outdated type of digital vocoder 20 years ago, its still "bad"...Your comparison of the 1999 digital vocoder to the 2018 vocoder is like comparing apples to an aircraft carrier.
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.