The meaning is the same in England as fdmaxey says. to be mean can also imply that they won't spend any money unless they really really have to.

It means that "they" (whoever "they" are) stopped being rude, unpleasant and unfair to everyone. The phrase is used by both the American and British, though more by the Americans I think. Someone from Britain might want to correct me on this. The older usage of "mean" was base, shabby or of inferior quality. However, it is not used that way much anymore.

Actually, this phrase may be only spoken in North-Central Alberta, Canada. It is understood nowhere else in the world.