Welp... that's quite a capable piece of surveillance.
I imagined it involved tapping to cell towers/cell infrastructure, but the details at the wikipedia page [1] suggest servers were hacked instead? Did they hack AT&T servers or something?
Side note, are there any ways to not get your data stolen in such cases? I would imagine using only a VPN might help, but if they're getting data from triangulation you couldn't do much short of turning off your phone, right?