The phone may have been off-hook. It is not that uncommon that people do not replace the receiver correctly, causing the line to be still active. The other alternative was that Security broke into her flat first, replaced the phone with a hacked one and tapped her line before it reached the exchange. It is inconceivable that a communist country with public exchanges working with step switches and relays could have targeted a random telephone number this way.

Today's technology is miles away from that. Everything is digital, so listening in on random (or, indeed, all) telephone calls is a doddle. Storage is not a consideration either: nothing is on tapes anymore, everything is in massive disk arrays. So they do not have to care about pressing the record button, they can just record everything and retrieve the info retroactively as and when they decide to focus on you. It is better to assume that they do and not use your phone - mobile or stationary - for anything sensitive.

Whether there are any backdoors in mobile phones that allow the authorities to monitor your audio while the phone is seemingly idle - I don't know. Could that be why my N900's battery runs dry after two days? Anyway, I wish them good luck with that. It must be terribly boring to listen to my phone.