Ah! Found it: although Yates told the House he had the mobile operators inform the hacked, and named Vodafone and Orange, he didn’t. Specifically, Orange identified about 45 victims but didn’t tell anyone. Vodafone identified 40 and only told a few who were considered VIPs. T-Mobile UK claims not to have found any. 3UK isn’t mentioned. Only O2 is known to have informed all of theirs without waiting to be asked. I therefore presume that the operator that has logged all the lawful intercept requests back to 2009 is O2, although I don’t have any further evidence for this deduction.