BGA Official :

A safe restart of BGA is our top priority, along with ensuring production of the highest quality vehicles for our customers.
Thanks to the incredible efforts of our employees at the plant coupled with the additional assistance from other GM manufacturing locations, restoration efforts of the facility have quickly progressed this week, and Bowling Green Assembly is on track for a cadenced return to work starting Monday, Dec. 20.

As to damaged, ordered C8s :

If a customer’s order was impacted by the storm, the customer will be contacted by their dealer and their order will be prioritized and re-sequenced back into production, with an expected production date as quickly as possible after the plant resumes normal operations.