Import? Sure.
Edit? not so much.
It depends on which codec – and Perian is a great swiss army knife to view different AVI files. If QuickTime can see it, FCP can see it.
But you’ll find that when you drop AVI’s in your timeline, that you’ll have to render everything just to even play your files. It’s probably best to transcode using compressor to something that’s video editing compliant.
Best,
Jeff G