I think it is save to assume, that if an intelligence service is putting the effort into intercepting your email communication, they are most likely willing to

I think it is save to assume, that if an intelligence service is putting the effort into intercepting your email communication, they are most likely willing to intercept your telephone communication as well. Voice recognition software has been around for ages, and mainstream consumer products (DragonSpeak, etc) have become surprisingly good. Sure, they could have used prepaid mobile phones or voice scramblers, but then again they also could have just accessed their secret email account(s) just from public access points.