I believe there are uptick rules to consider - i.e., The company cannot do a buy if the transaction creates an uptick in the stock price, or something like that.
If you think about it, it kind of makes sense - A company should not be allowed to pump its own stock by manipulating the price.
I am guessing that if there is buying pressure at the ask, then the company will be able to purchase some stock at or near the ask since this would not be creating an uptick.
...hope I got that right. GLTA