Ottawa seemed to be used primarily when it first started showing up for outland apps.
It was very active and busy in December. And even some DMs and other movement, but seems to have stalled for passport request since then.
This also seems related to Minister's announcements about hitting some targets by end of 2020. Also Mississauga has stalled (not entirely but a lot of complaints).
Right now it's not clear, possibly Ottawa was a temporary thing and there are a lot of files moving from Ottawa to country offices.
"Regional VO" - if you mean in-country, there has always been a split between files processed at offices in Canada and offices abroad. For various reasons that are not always clear. Just capacity or complexity or other reasons. Apart from the speed - utlimately it doesn't matter to the PA as the passport request will still be done and the visa/COPR printed depending on where the applicant is physically.
Ie. if Ottawa issues a PPR and the applicant is in Delhi, visa office in delhi (Australia, Warsaw, Hong Kong, doesn't matter) will physically do the visa/copr. If the applicant is in Canada, the process - right now more like a virtual landing since no visa needed - is done in Canada somewhere.
That said: roughly some countries always have files done in country offices (eg Russia done in Warsaw), and for those countries that use the Canadian visa offices (ottawa, mississauga) the files that were kept in Canada for processing were 'less complex.'
Covid is messing these things up though, changes being made, offices that were fast used to be slow and vice/versa, etc. Lately they have started sending a lot of files to Shanghai - even non-chinese ones - presumably because there is extra capacity there. Likewise London sending files out - covid lockdowns in the UK.
All of that said - this is all changing as they try to deal with covid. Very few firm conclusions can be made. People used to be happy to get their files sent to Mississauga and then Ottawa, lately everyone is upset with those offices.
