The easiest way to find out if a rate is publicly available is to go to the Marriott website, but do not use your MR # to log on. Also do not select any special or corporate rate box. Select your hotel and date...if a rate visible, it is publicly available. If it is not....it is against the T&C's of the BB.

There are times when hotels will accept a BB on any rate, but best not to count on that...