It seems that the Vancouver office 'owns' (is called primary) files when they do security screening (as far as I can tell, that means for all files, although possibly ones that get semi-automatic clearance or lowest level either aren't attributed to vancouver or only for a very short period of time - which would look the same to an outsider).
After that - again, as far as we can tell - it goes to 'local' offices for the oath etc.
In other words - it's not that we got unlucky by having our files sent to vancouver; if Vancouver does all the files for security (or for those that have longer screening) - it's not 'Vancouver' that's slow, just the security process.