3-4 months to get AOR then 1 YEAR to get a transfer to a local consulate. Then things start moving slowly from there. Mine just got transferred to local consulate after one year of submission.
The letter which you received from the CIO - Nova Scotia is not called AOR, it is an assessment letter.
you will receive a letter from Buffalo called "AOR" after they receive your complete application with the supporting documents, the average to receive the AOR from Buffalo is 3 weeks to one month (some people take longer to receive it).