i've covered MTVAA for 2 years now, and i can honestly tell you, unless you go to the red carpet area (the stretch of area from where they stop their cars and walk into Indoor Stadium) very VERY early, you won't stand a chance to take photos against the sea of groupies. and that's the only area you can take photos of the celebs. inside the performance areas, no photography is allowed at all (i'm not counting micro cams and phone cams) and lauLEE is right, they're very VERY strict about this. even the official/press photographers can only take shots inside a designated Photo Room (which not all celebs will come; some are atas enough to skip it). no one is allowed to inside the actual stadium to take photos, except the official broadcasting agency (e.g. MTV).
2 things to note: not all celebs will go on the red carpet (most of them do, but there are exceptions), and go recce the place early, cos the red carpet area changes from year to year. also, and don't bother with long lenses. you're normally crushed up so close to the celebs that ultra-wides are advisable.