It's impossible to get a straight answer. I am on Sprint. They made a big deal about being the first carrier to roll out CMAS. None of their techs know what I'm talking about. My 4S now has notifications but there's no way to find out from Sprint whether or not they're supporting it.
The facts as I know them:
1. Sprint supports the service on some phones
2. iphone is not listed on any of the services
3. Apple supports it on their phones, though the carriers of course have to as well
4. The government has mandated all carriers support it eventually
5. We just won't know if it works until it works
Very frustrating.
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They took the feature away? I thought the government says everybody has to have them.