Yes, they have. The rationale being that they were giving their customers something extra by introducing a select group of services that were exempt from pre-existing data caps. I'm sure a lawyer could argue that it was all perfectly legal, but it nonetheless looks like they've been violating net neutrality in spirit for quite some time.

AFAIK, cell companies were never under the "net neutrality" regulations, which is something that's often not made as clear as it probably should be in these discussions. Also, T-Mobile is doing is called "zero rating" in industry parlance, and I think you're correct that zero rating would have been legal under net neutrality regulation even if it had applied.

What they’ve done is somewhat different, offering exemptions from the normal metered service for certain classes of activity like music streaming.

The base rate hasn’t changed and the category exemptions were open to anyone in a market rather than being negotiated behind the scenes.

I’m expecting that’s going to look really good compared to what we’re about to see.

Actually, FCC has chimed in on this 'zero rating' https://www.theregister.co.uk/2017/01/12/new_fcc_guidelines_...

FCC liked what T-Mobile was doing with Binge on because it didn't favour particular services or alter consumer choice significantly. It was fair and open or any website to participate in

> When it comes to T‑Mobile US Binge On services, FCC staff decided that the service "did not compel edge providers or consumers to participate in Binge On, and did not charge them anything if they opt to do so" – and therefore was legit.

> However, AT&T's Sponsored Data program "presents competitive problems" because it "imposes hefty per-gigabyte charges on unaffiliated third parties for use of Sponsored Data" – charges that "far exceed the costs AT&T incurs in providing the sponsored data service."

> FCC liked what T-Mobile was doing with Binge on because it didn't favour particular services or alter consumer choice significantly. It was fair and open or any website to participate in

In Netherlands T-Mobile has a unlimited music streaming offering. To participate, a contract needs to be signed. Plus the organization/company signing such an offer needs to sign a paid support contract.

Meaning: this option within Netherlands is not free, not fair, not open. Apple refused to join that scheme in the Netherlands. Due to that new information there's going to be a new legal case about it.

Binge On biases video over gaming and apps and videochat. That alters consumer choice significantly.

I belive cell companies where either entirely, or partly exempt from net neutrality.