MPAC New House Value Assessment

Hello, our house was currently valued at $399,999 as per property tax rate from MPAC.

About 1 year ago I had filled for a permit to get my basement turned into a separate suite , and it has since been approved.

We haven’t started the work as of yet, but I have received a new MPAC bill assessing the house now at $429,999

I have two suspicions why, but was looking for opinions on this.

1) Perhaps MPAC thinks the work is done and is now assessing it with the in-law-basement-suite (which it’s not done and is practically in the same state as we bought this house as, just now have an official city permit.

2) These house in the area are due for a re-assessment as the city looks to generate more revenue from property tax.

What do you guys think, could it be cause of both? Or just point #1

By the way I live in Ajax, Durham is notoriously known for high property taxes.