I just got my CeleronII 850/100 today and Im running it @ 133MHz FSB, I didn't even try to start it with 100 MHz FSB. Immediately to 133 MHz FSB.
Im running mine at 140 MHz right now which gives me 1190MHz - not bad for a cheap CPU.
So I think you should be able to get it up to 133MHz, even if I'm not running it in a BX-board (I have a VIA-board).
/steimm