This seems like a loss leader [1] for T-Mobile. Despite your theoretical indie label service it doesn't have anything to do with net neutrality. T-Mobile deciding to forego revenue as marketing gimmick is different than T-Mobile double dipping by charging streaming service providers to utilize capacity the customer has already paid for.
> Despite your theoretical indie label service it doesn't have anything to do with net neutrality.
I respectfully disagree. Net Neutrality is not simply about carriers charging for" double dipping. It is, at its heart, a free speech issue. It is about certain forms of speech being treated with economic preference. It is about maintaining the low barrier of entry that makes the internet so valuable.
I don't see how they are "treating" data from Rhapsody different than how they are treating data from XBox Music or Beats differently when examined at the network level. This promotion is at the accounting level only. When the two become intertwined like Netflix/Verizon/Level 3 peering drama then I agree with you. But unless somebody can demonstrate T-Mobile degrading the quality of the network traffic for non-Rhapsody streamers I don't think this has anything to do with net neutrality.
There is a line between marketing/cross promotions business relationships and encroachment on net neutrality, consumers need to be vigilant, but the line does exist.
They are treating Rhapsody data different from Hacker News data. Or data from my personal blog. That they are consistent among their partners is irrelevant.
[1] http://en.wikipedia.org/wiki/Loss_leader