I just depends on what the phone hardware supports. The Nexus 6 e.g. has two hardware variations. The US variation supports T-Mobile, AT&T, Verizon, and Sprint

I just depends on what the phone hardware supports. The Nexus 6 e.g. has two hardware variations. The US variation supports T-Mobile, AT&T, Verizon, and Sprint all with the same device. http://www.androidpolice.com/2014/10/15/the-nexus-6-will-come-in-two-versions-for-the-americas-and-rest-of-the-worldhere-are-all-the-supported-bands/ http://www.androidpolice.com/2014/10/15/the-nexus-6-will-com...