I noticed something interesting in the Ultimate Alliance Program Files. In Program Files > Activision > Marvel - Ultimate Alliance > motionpaths, there's a folder called "abyss." I opened it, and found several files that are all have blimp in their title (ex: blimp_fly_in.igb). It's rather interesting that they'd have that in there, seeing as how the abyss blimp battle was in X-Men Legends II. Although, now that I think about it, they could've used these files for something else, instead of recreating the files.
Right as I posted that, I (maybe) figured out what those were used on: the little crafts the Ultron Bots use in the Helicarrier mission. They fly up, shudder, and explode very similarly to the way the blimps do in that battle in Legends II.
You'll notice that most of the files from X-Men Legends 2 are present in Marvel Ultimate Alliance... I think that's because MUA uses XML2 as base.
Magneto's Ultimate for example
Yeah, a lot of XMLII files are in there. The game was used as a base and some files just weren't deleted at all despite not having any fuction in game.