I think it's referring to the master character list here: http://yuletidetreasure.org/nominations/charlist.txt. That list has nothing to do with what's been nominated so far, though - it's the list of all fandoms that have ever been nominated at Yuletide, and the characters in each fandom. I don't think it's dynamically updated, but don't know for sure. So, the deal is, if you nominate a fandom that's been nominated before, it will automatically populate with the characters that have been nominated before. So you can check that list for the characters you want, and if a fandom that's been nominated before has been nominated again this year, you can be relatively sure that the characters that were nominated before are nominated again.

However, if you're worried about Character A being nominated, the safest thing to do is still to nominate the fandom and character yourself, since there are several points of potential failure within this process.

I hope that made at least a little sense!