There will always be, of course, room for differences of opinion about the importance of a particular piece of information, and the markets will not always be able to pick the exact interpretation the decision makers will place on it. Hence there will be some surprises.
Nonetheless, given a good understanding of the framework, which I think now  4  BIS Review 84/2001  exists, there should normally be a reasonable degree of predictability of the general course of action the Bank will take over time, even if not necessarily month by month.