It didn't work well. It stored encryption keys centrally and because of that the police was listening in for months without anyone knowing before they shut it down.
For an encrypted phone network that's pretty much the opposite of working well. Even with the servers compromised the network should remain secure. Like it is with Signal and even WhatsApp.
I always wonder why such networks make mistakes like storing key material centrally. I suppose telling a crime lord that he can't have his messages back because he forgot his PIN code is not fun. But neither is having their network cracked by the police I guess.
