I do not know if this is intentional or not however I do not see an option to disable it anywhere to I will assume it is an unwanted feature or a bug. When connecting to server TeamSpeak will mute Spotify's audio stream. This only happens on Linux, I was using Ubuntu specifically. You are able to go into the audio settings in Ubuntu and click the toggle again to turn the audio back on however as soon and another audio stream comes into play TeamSpeak will cut off Spotify again.