WGGC was back on the air by at least Thursday afternoon around 5pm. However, it was not airing regular programming. It was airing a syndicated country Christmas show. The area of WGGC's studios, which is a highly trafficked area (US 31W By-pass) remains closed to traffic. I am not a regular listener of WGGC, and at this time I am not sure of the programming.
WBKO went off the air when the tornado hit. The studios are VERY close to the Creekwood subdivision where there were many of the fatalities. I am not certain how long they were off the air because we lost power at our home about 5 minutes later as the tornado tracked through the city. WNKY was live on the air with weather coverage up until I lost power.
In the aftermath of the disaster, WBKO was without internet connectivity due to major fiber cuts in the area and lost carriage with Youtube TV for WBKO-ABC until about midweek. WBKO-FOX feed was not impacted strangely enough. In fact, during the period, WBKO aired their local newscasts on both ABC and Fox feeds.
Somewhat ironic, WBKO-ABC was pulled from YTTV for a carriage dispute with ABC/Disney right in the middle of the disaster recovery - this should have been a consideration before Disney/ABC and YTTV shut off the channel with all the others nationwide. Not good PR to say the least.
There may have been downtime for WNKY and WKYU (on-air and/or online), but they were both on-air when my power returned around Noon Saturday (the day following the event).