You are talking about 2 different worlds, the TETRA you have is mostly privately owned, not a common practice here in the U.S. YET. I don't believe that a private company should control the radio comms of Public Safety. P-25 is not a commercial format, even though it is becoming one. It was designed by Public Safety professionals for Public Safety after many years of testing. It relies more heavily on error correction, because it needs too. If you lose a word or 2 on a private call it's no matter, but in Public Safety that would be a issue very quickly. There have been plenty of TETRA failures right in London that have made international news. There have been very few here with P-25 none of which I am aware of made international news. TETRA has it's uses but in my opinion it hasn't grown up enough to compete with P-25 as a true Public Safety radio format. TETRA is very infrastructure intense, meaning it needs a LOT of radios sites, more on the order of a cell system, and other than it is being unmonitorable, which China I'm sure wants due to it's draconian attitude towards it's public.
TETRA may have it's place in commercial and industrial communications, but I wouldn't want it for Public Safety.
Oh BTW NYC Transit is PLAYING with TETRA right now, I don't have anymore info other than that.