You won't hear the beeps on recorded data/playback... but only when the recording takes place. Try calling someone and the moment you establish connection, Press "menu" and scroll to "record" and start recording the telephone conversation. You will hear consequtive beeps every 20 seconds and the other party will also hear the same thing. (to ensure that they are aware that the conversation is being recorded by your phone)
To what I've read and understood, the beep sound file is embedded into the firmware and the patch mentioned above only removes the sound on the recording phone but still continues to beep on the other party being called.