For the time being, you’ll be paying the property tax based on the previous value. Some time next year, possibly in the summer, you’ll get a refund check from the tax assessor based on the difference between what you did pay in taxes and what you should have paid if the house were reassessed in time.
Once the tax assessor comes around to reassess your house, you’ll may need to contact the escrow company and tell them to reduce the amount they collect from you every month.