i'm pretty sure it does but am not 100%..
I have some mpc60 disks (they have everything on those, seqs, songs, samples, params, everything.) and I can put those disks into the 2000 classic and they work. they take a bitching long time to load but they will load. the problem is the sequences get slightly messed up but are fixable.
therefore, I'm sure the 3000 will load in the 4000 except as I had to... you may have to rebuild the song. (by the way I just turned off the classic and kept that song in the 60 floppy to use on the 60)
MPC-Live/Remix16