According to several sources (see: http://en.wikipedia.org/wiki/Disk_II#UniDisk_5.25.22_and_Apple_5.25_Drive and Google your way around the rest...), Disk II controllers and Apple 5.25 drive (Or UniDisk 5.25) controllers are completely compatible. Conversion cables exist in both directions without anything fancy - one connector per end, no extra power taps etc.
So - the -12v line is present on both, and the drives are interchangeable. We know that so far. Whether the drive itself uses that line internally is unknown... There could be variations there. But the interface and cabling standard maintains the -12v line into the drive cabinet.
**EDIT: According to the page at http://www.vintagemacworld.com/drives.html, section "Apple 5.25" Drive (A9M0107)":
So - the -12v line is present on both, and the drives are interchangeable. We know that so far. Whether the drive itself uses that line internally is unknown... There could be variations there. But the interface and cabling standard maintains the -12v line into the drive cabinet.
**EDIT: According to the page at http://www.vintagemacworld.com/drives.html, section "Apple 5.25" Drive (A9M0107)":
So, it seems that the UniDisk 5.25 drive and Disk II actually use the -12v, and the "Apple 5.25 Drive" does not - the LC IIe Card doesn't provide it, and therefore is only happy with the drive marked "Apple 5.25 Drive" (Part # A9M0107). I would take that to mean that a IIe without -12v available would have the same limitations.