Can't you just use DBAN on the PC or whatever you use to erase the disks? It makes no difference if they've been used on a Mac. Also, an LLF does not really erase data. It just rewrites some sync tracks and stuff. The data is still on the platters.
Edit: In fact, you can erase disks from just about ANY platform with this way. IBM RS/6000, Sun, SGI, Mac, PC, pretty much anything.