There is nothing about the N900 or Maemo that Microsoft would have any interest in. The hardware is old and obsolete, the design is nothing like what Microsoft wants for Windows Phone (does anyone even make hw-keyboard phones for Windows Phone?). The software is totally different in the way it works to anything Microsoft has (the kernel is different, the middle-ware is different, the UI is different, its all different)

About the only thing from Maemo or the N900 Microsoft might want would be any patents and it would only want those so it can shakedown its competitors for more royalties.