Forgotten Bases aren't infected, only outposts and camps. There is a criteria set for spawning them relating a tunnel and POI - you (or your alliance) need to be in control of both within the expected +/- figure of your offence. I'm not sure of the exact criteria (although someone will probably tell us!).
Unfortunately you'll have to be content with a badge of some sort. The money side is controlled tightly by EA and the only event they seem to pay for is the much maligned World Championship Servers.