They're compatible as far as the spline interface goes (I used to have Ultegra cranks with a XTR BB) but the chainline will be a few mm off and you may have chainstay interference. You can find the XTR BBs on ebay for ~$30, so it's not a big deal if you need to change the BB too.
Terre Haute, Lafayette, or Indianapolis, IN, depending on the day
n, I would like n+1
Just be sure in case you go to other mountain bike octalink BBs that they are all V1 as V1 is not compatible with V2 (longer splines among other things). As for the two you mentioned, the xtr one is 3mm longer (as labeled in the pic, 109.5,112.5) and so your chainline will be too wide.