In addition to each carrier testing to see if the update works properly on their network, the update is offered in waves, so as not to congest the network. Users on the Telus network will receive it at various times, as did those on the Bell network.
If you want upgrades as soon as possible after release you need have an iPhone or Nexus purchased directly from Google. Both of those lines are updated from the supplier servers, rather than the carrier's.
NFtoBC
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