No, Christine isn't there during the auction scene. Just Raul and Giry.
In the movie they are showing you two stories at once. The musical of course. And, then there are bits in black and white that show Raul bringing the music box to Christine's grave. At the end when he gets there you see one of the Phantom's red roses. So, at least as far as the movie is concerned, the Phantom doesn't die. You don't know of course what point in time he left the rose there. It's just there.
I also think that the movie made better use of the roses that you see in the ad. In the movie they came with every one of the Phantom's notes. In the show it doesn't mean anything.
It's true that your not supposed to think much about what happens to the Phantom other then he disappears. But, with the wonderful (said sarcastically) sequel coming up Webber will do a good job of changing that.
As for me saying that Christine is alive during the auction scene was nothing short of a total brain fart. I have seen the show 8 times and I should have realized that. Sorry.
"If you try to shag my husband while I am still alive, I will shove the art of motorcycle maintenance up your rancid little Cu**. That's a good dear"
Tom Stoppard's Rock N Roll