Well, about the time I pushed the button on the above post the frameset arrived.

With Conti Grand Prix 700x24C tires mounted on Ksyrium Elites a quick and dirty measuring shows:

BB height: 265mm
BB drop (from geo chart): 73mm
Clearance at 320mm on stays and fork: all about 40mm

I don't think this is a candidate for 650B or 650A conversion

I don't have any 25 or 28mm tires handy, I'll have to grab a couple cheapies and see what I get.