Not quite - CALEA legally requires telcos to cooperate with law enforcement and implement infrastructure for wiretapping. As far as I'm aware, no such law appli

Not quite - CALEA legally requires telcos to cooperate with law enforcement and implement infrastructure for wiretapping. As far as I'm aware, no such law applies to Microsoft as they aren't a carrier under said law. So any eavesdropping Microsoft lets law enforcement do is voluntary, whereas telcos have a legal requirement in this regards. Metadata (call logs and such) is another story and are equally unprotected in practice.