Is it the author that decides if a character is a 'guest-star'?
For the purposes of the Archive, it's usually the EIC.
We usually say that LNC must feature in at least a third of the story - but that's mostly to ensure that we don't get submissions from authors trying to get Superman stories past us where LNC only feature in one line.
Generally speaking, it's a lot more fluid than that. But LNC should be strongly represented because we are, after all, first and foremost, an Archive for stories about the LNC universe.
I've quickly skimmed a couple of Lara's stories and, yes, I'd definitely say that Batman is strongly enough featured in the ones I read for those to be considered crossovers.
LabRat
