I asked my "Delivery Specialist" after a year of ownership. He gladly gave it to me.
I now have my Slacker favourites synchronized across my Sonos speakers, tablet, phone and computer. The only catch is it doesn't work on my cellular data connection here in Canada. Slacker logs me out if i try to connect via a cell phone not connected to wifi.
My new question to Tesla is if I can carry that same account over to my new Model X when I get it. It'd be a shame to lose all my favourites and start over.