What's likely going on is that the campaigns have data they are using to measure their own performance based on expectations that they do not release to the public (the kind of thing that was stolen in Watergate).

If they are confident there are x ballots coming from y precinct and those ballots are breaking in their favor by z%, they'll make a statement like this.

For the news media, they have to wait for official returns for recounts and things like that to become publicly available.