Martin said Wall has already paid his fine and completed the counseling and the hours of community service mandated by his sentence. He likely will seek an early discharge from probation, Martin said.
According to Clayton County Magistrate Court records, police said they found Wall and Michael Reid Pettry engaged in oral sex in a restroom at Hartsfield-Jackson International Airport on March 13, 2007.
They arrested both men on public indecency charges.
In February, Pettry, of Indianapolis, pleaded no contest and was sentenced to 12 months of probation, a $500 fine and 64 hours of community service, according to court records.
At the time of his arrest, Wall was chairman of the MARTA board. He has since resigned as chairman but remains a member.
Wall was fired as Clayton County's financial adviser in January. He previously advised Clayton periodically since 1988 and was hired as the county's investment banker in October.