Addition to UMG's perspective I want to add another comment from a major label executive:
"...if a service can verify that a user has purchased a song (i.e. The service is Apple and they know the track was purchased through iTunes), then they should allow that song to be used on multiple devices. If a service can not verify that a song was purchased, a consumer should be charged a monthly fee, shared with labels, for multi-platform access."
I wrote my masters thesis on cloud music services and this is what I got from a personal interview question on the meaning of a streaming of single purchases.
I believe that majors are after subscription fees and if Apple was to limit its cloud service to legally purchased songs it wouldn't be having so much of a trouble with licenses.