Called, good, Not called, not good. They won't call if you didn't make the cut at the interview. If they called, you made the cut, now your'e getting checked out to go to the next level. Some problems are discovered during background checks, this will be voted on at the hiring board. Just because you get a reference called, doesn't mean youv'e made it, it's just an indicator your proceeding through the process.
There have been a few who say their referencse were not called yet they were hired. I disagree, they just didn't know who the PD folks talked too.
So, don't give up hope.