There isn't AUX in as standard, but at the time, there was a dealer-fit interface called the Audio Connectivity Module (ACM) - it works by simulating the CD changer and provides aux in and Apple music controls as well as a USB in. They come up for sale occasionally.
If you have a look in the ICE section there is a lot about a possible replacement system using an android tablet.
My car has a Bury hands free phone kit which also streams music, however it uses the Bury Amp and it's not as powerful as the factory system or as good sounding as the CD - and it cuts out the factory stereo so you don't hear the sat nav.
My previous X350 had factory bluetooth but that only worked for calls not music.
If you have a look in the ICE section there is a lot about a possible replacement system using an android tablet.
My car has a Bury hands free phone kit which also streams music, however it uses the Bury Amp and it's not as powerful as the factory system or as good sounding as the CD - and it cuts out the factory stereo so you don't hear the sat nav.
My previous X350 had factory bluetooth but that only worked for calls not music.