Not sure I know with other phones, like the Z10, the update was put out by the carriers simply. If you had Telus you would get their update, if you had T-MOBILE you would get theirs.
Either way I suppose you can always root and load what ever you want on it. That's what lots of people do when the phone manufacturer/carrier stops support for that specific phone.
I am not an expert though maybe someone else could chine in here that has more experience
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