Well, the carriers are giving THEIR encryption keys to the NSA. . . but not to crooks. Oh, wait, maybe NSA and crooks are one and the same, depending on one's definition. Apple's iMessage encryption is not shared with anyone.
The ability to decode any encryption depends on how complex the key is. . . a sufficiently complex key can take years or eons to unencrypt. If the Carrier's key is simple, and the data is sufficiently repetitive, it would trivial for anyone to decode it. I suspect the level is not too high.
I’m a big fan of privacy.... but I’m just saying...if they track my cell phone they’re gonna get.... “hey, my car won’t start. I need you. Okay, I’m on my way with jumper cables”. Or.... “Hey, I need you to play guitar in our candlelight service”. “Okay, be glad to”. Or..... “What time are we going to play golf tomorrow? I have a 10 am tee time”.
FWIW, for the past 10+ years, I’ve used PGP/GPG with a 4096-bit key for anything I want to keep away from prying eyes. Nothing less is trustworthy, IMO. I’m 63, and I’ll be dead before they’re able to crack a 4096 bit encryption. Or if I have the good fortune to live long enough to see that threshold crossed, I’ll bump it up another factor of 2 and re-encrypt the stuff I care about.