Hi. Recently attended oath ceremony at Mississauga in March. Ceremony itself will start around 9 -9.30 am depending on how many persons are going to take oath. In our case, there were 114 persons.
Ceremony itself will take one hour or slightly more and by the time you finish and take some pics etc, it will be 11 am before you can leave.
If you are going to take your car there, park at the back of the building because the citizenship ceremony entrance is at the back
All the best.