Know of any figures for how bright the flares from it actually are?
I don't know, but we can do a quick estimate. Judging from the picture, each surface seems to have an area similar to a circle with a radius of ~12 cm. Let's assume a distance of 200 km, that gives an apparent size of 0.000068755 degrees. The Sun's apparent size is 0.5 degrees, so the diameters differ by a factor of 0.00013751 and hence the area by a factor of 0.000000018909. If we assume perfect reflection, that translates into a magnitude difference of 20.7, so at 200 km distance the upper value for the brightness comes out as -6.