Currently have numerous G and H Units going 10-8 with Gulfport and Hattiesburg on 700 mHz system for contraflow drill. Hearing it on 764.40625 Control Channel using voice channels 764.656250 and 764.90625 south of McComb. This may be a FEMA system (as per previous posts) but all units heard this morning are state units. According to a press story, MDOT personnel will be handling the drill. Those using the system this morning sound very proficient in the use of 10 codes and "sound" like law enforcement personnel rather than highway workers.