I'm no expert, but what is so wrong with TETRA anyway ?
It's here, it's a mature technology, most of the bugs are now quashed, everyone is used to it,
it's a 4 slot TDMA system, and has strong TEA2 encryption.. so why change ?
TEA2 hasn't been cracked and handsets are easily and widely available.
So WHY change it ? For some paperwork, contract sillyness, or just plain corporate greed ?
or the promise of more and better.. Look when P25 (phase1) was started in N.America and Aus, there were many problems, security failed, and many depots went back to FM and when these (nice but limited) FDMA P25 phase1 systems were in place, TDMA systems started to make FDMA look rather silly, so P25 phase2 - a 2 slot TDMA system was launched to counter that. the French 3 slot TDMA 'Detracom' (IIRC) went by the way and TetraPol and DMR seemingly reigned.
Motorola are the radiocomms equivalent of miserable Apple nowadays, and, though the hardware and software is usually excellent (with the exception of some of the crappy DMR firmware fails) Moto's famous heavy-handedness, litigious, nastiness, greed and screamingly overpriced price-hikes (when it comes to sucking public money from the public purse) is well known in certain circles.
Although i'm no expert in TETRA, I predict great fail for the replacement, and perhaps, just perhaps, an hurried, under-the-table buy up of cheap DMR gear to fill in the failures might happen temporarily if the new tech fails (imagine that) maybe lending creedence to the (rumoured) UK-wide trunked commercial DMR network, but that may be vapourware..
Blue-light services need reliable comms, and sadly, encryption, and what they don't need is more complication, on a larger scale, society is becoming even more complex and is failing (entropy?) and any engineer will tell you that increasing complexity is no way to increase reliability.
If the central system fails, and it really can, we will *really* need these folks, Yes of course there are backups and generators etc, but there needs to be independant, off-the-grid type systems available too, as fallback.. I hear rumours that *some* blue-light services still retain a *little* old equipment just for this reason, and i personally suspect (and hope) even some of the old MOULD hilltop sites are still quietly maintained, even though much of that ancient gear is sold off to Hams & off to overseas developing countries.
Maybe chinese built USB hardware just won't cut it, with clumsy touchscreens, battery life issues, OS security, chipset vulnerability, crappy USB accessories, chinese wiring & chinese connectors perhaps,
I they'll never need to download an app to arrest a gun toting felon or walking through a burning building with floors they're walking on, collapsing underneath them with this over complicated stuff.. a gross and silly simplification of course, but sometimes a simple PTT system is best..