Yup, Ballast is right. The guys spend an incredible amount of time training specifically for their sport that weight lifting is second. A friend of mine trains with teh Lion's Den crew in Dallas and the guys typically lift about twice a week concentrating one day on explosive work (oly lifts, depth jumps, speed lifts) and one day of strength training.
There are times they will go more frequently but a lot is determined by how far out their fights are. They'll also typically periodize their training between absolute strength and funcitonal hypertrophy (depending on weight class allowance and time to next fight).