According to the PC Pro Microsoft have confirmed it is preparing to launch a music-streaming service in the UK. In the The Telegraph, Peter Bale, executive producer of MSN claimed: "Music is an important area for Microsoft. We are looking at launching a music streaming service imminently. It will be a similar principle to Spotify but we are still examining how the business model will work."
No word on how it will work and whether there could be any Media Center or Zune integration but my guess is that it could be linked to the Xbox 360 dash.