is indeed partially streamed and partially sequenced. PSF_rippers now has a preliminary PSF2 set out for the game, and this explains why there were only about 20 songs I could find from the game data Bladegash sent me (which has since been lost in a dual-hard drive crash).
Edit: Eh, I probably shouldn't speak until I download... the PSF2 set only has 26 tracks, and they're all huge-ass files, so I can only assume that they're simply more streamed data in the PSF2 container. Whicih laeds me to a question I should have asked long ago, just how much of the Rockman X7 OST IS actually part of the game?