I am with all of the people who say, "Although the fangirl in me..."
... goes "DO IT, DO IT, DO IT, DO IT!!!", I know that Billy Petersen would be against it and would also refuse to have any sort of screentime with the peeps from CSI: Miami and CSI: NY. (Although the pic from that thingy honoring Jerry Bruckheimer where he was with Marg Helgenberger and Gary Sinise surprised me a bit...) I know this because I've heard it on the commentary from my S1 box set of CSI: Miami DVDs that he didn't want to hear from or speak to any of the CSI: Miami cast on "Cross Jurisdictions". (There's not a commentary when it's in the S2 box set of CSI:, but it's on the Miami S1 box set.) And I agree with
talyra: If they
do ever feel like making a three-way crossover, they should do it in a movie.
But if you read the article in the US TV Guide magazine back in August or September when Adam Rodriguez, Eric Szmanda, and Carmine Giovinazzo were on the cover, they said in the article to "not close the case on a possible crossover episode featuring stars from all the series." Well, "if the right storyline came along, I'd be open to it": Eric Szmanda.
So he's all for it if the right storyline came along.
But I, on the other hand, am currently trying to battle writer's block on a triple crossover.... It sucks whenever you come up with a story like that and then you watch your favorite movie 15 times over and you come up with an idea with another story based on it with 3 people from each CSI: show.