So in this post, quite a few years later. I'll share what I found, when I poked around on an old PSU I pulled out of an old scrapped IBM server. First off, some pictures
To utilize this PSU, you'll have to bridge the shorter pin (on my two units at least) to ground.
While poking around on this PSU, I found 5.5v on three commoned pins. I'm uncertain if these serve as 5VSB, but I'd imagine that to be the case.
Short post from here, but wanted to share.