Awhile back, when I was with Verizon, I went into the store a day early and tried to get them to sell me a Pixel. I had been doing business with them for awhile and the clerk decide to give it a try. No good, the phone wasn't even in the system yet. I'm guessing the computer was set up to forbid early sales of the phone....?
Great question, to which I'll also look forward in hopes someone can answer. Hadn't thought about that, but will be sure to bring a high speed USB-C to USB-C cable. In either event, I would recommend manually initiating a backup (Settings>System>Back Up Now) shortly before heading to BB, to ensure everything is to its latest.