They have published requests from the law enforcement and their responses to these requests. The only unencrypted data they have is the phone number, a date of sign up and a date of the last login. That is it, everything else is encrypted and they cannot access it whatsoever.
I can go to the corner shop/local garage right now, buy a SIM card for 99p and then buy a top-up voucher in cash to have a completely anonymous phone number.
Albeit is the UK in Europe again? 🙈
edit: where I would be worried if my privacy was on the line is I could also go to the local pawn shop / Cash Converters to ensure that SIM card isn't associated with an IMEI I've previously used and buy in cash a cheapo phone.
Same in a few other European countries. I'm doing it right now with a few SIMs. You can also go on holiday to another country, get a few temporary SIMs there for a few quid and fly back home with the "contraband". Really not hard.
I don't know if you're in the UK right now but I can tell you right now that I can go round the corner and buy a SIM card in cash plus a top-up voucher, from someone like this guy
You also don't need to show any ID for a business to meet "know-your-customer" regulations. Can you get a phone number without revealing your identity?