As already answered above those which looks like to be easily approved or smaller/less complicated files are sent inside Canada even to a diff vo as a work sharing plan. But all such are not lucky as ours was sent there too, now taking rather more time by going to 3 diff offices..
Agree overall but there's more to it - some countries always go to country offices. And there are probably other things going on, as we know that sometimes they 'load balance' by sending to offices that are less busy (at least initially).
As someone else said, being sent to Ottawa (for example) is not a guarantee it won't eventually get sent on as someone at a later stage decides it's actually a more complicated file than it seemed at first - or other changes like due to covid. And if country office ahs some specialised knowledge/personnel that's needed for that file, being sent to Ottawa won't make it faster.
Put differently: fine to be happy if file is sent to Ottawa; but that's more a function of the file and their internal procedures, NOT a you-won-the-lottery-ticket moment and therefore it'll be faster.
(And by the way pre-covid it was mostly files being sent to Missisisauga like Ottawa now and those who had that happen were happy - and then Miss office slowed to a crawl, probably covid related.)