If this happens as expected it will be another feather in CalFire's cap, placing another tool in their aviation toolbox alongside the DC-10 and thier fleet of S-2's. Earlier this year the U.S. Forest Service signed a call when needed contract for the huge Martin Mars, which has been used quiet a bit in northern California this summer in the Seige of '08.
Capacities of large air tankers
Martin Mars: 7,200 gallons (water, retardant, gel, or wildland foam)
DC-10: 12,000 gallons (water or retardant)
747: 20,000 gallons (water or retardant)