How does IRCC choose your visa office? Mine is ottowa but but like how did applications go to Mississauga? Is it based off of where you plan to land?
Whatever works for them. Prior to covid, it was mostly either regional visa office for the applicant OR mississauga office. In general terms, it looked (from the outside) that somewhat 'easier' files went to Miss, but for some countries, always went to field office.
Now - they are mixing things up a lot. Ottawa is new. Some files going to Shanghai/Beijing seemingly because some extra capacity there. Mississauga seems to have had the longest covid delays (presumably lockdown). London office sending files to Warsaw and Vienna, also presumably for capacity/covid reasons.
Also reading between lines more sharing of work between offices perhaps because of more online/digital work.