Another thing to think about is this: Movies as textures. I know how to work it in Maya, and someone that was in my animation class who used Blender as their main program said that it was also possible in Blender. I think this was discussed somewhere else here, as the point of animated advertisements came up. It could also be used for computer screens, etc.
This is extremely easy in Blender for Blender's own rendering engine (good for animated cut-scenes and cinematic clips and such), but as Mattn said it wouldn't work for models in UFO: AI because animated textures wouldn't export to MD2 format (I don't think MD2 supports such a thing).
...But if I don't export to MD2 and render something from inside Blender, yes, it is very easy, all I have to do is go to the image selection for a material that would normally point to a still graphic file (JPEG, PNG, BMP, TGA, etc.) and instead point it to an AVI or MPEG or such, then tell it which frames to use from the video clip. Not only that, but I can also have it use/calculate an alpha channel and mix it with other textures or make parts transparent, etc.
I've actually done this before, yes it is very easy and impressive, but as I said it only works internal in Blender for direct rendering to a video clip, not for export to a game engine like the one used for UFO: AI.
Some of the newer game/3D graphic engines that have come out more recently
do support video clips as textures though, for example the Irrlicht engine (you can find it on sourceforge) supports video textures for imported models, and is frequently used for games coded in C++. The older quake 2 modified for UFO: AI is a different story, and I don't know if it ever could support this if modified further or not.