One of the places I work as a freelance editor has several Mac Pros that are currently running CC 2014. They are air-gaped from the outside world (big company IT policy) so every few months we use one of our phones to tether and connect to the Internet so CC can call home and stay activated. Works fine.
We would like to update them to to CC 2015, but it's SLOW using this option. Is it possible to download the installer files on a different computer, copy them to a drive and then bring them in and install them off the drive and then use the iPhone tether just to activate everything?