The Vasari Corridor finally reopened two days ago since its closing in July for "fire hazard and fire safety" issues -- yes, it is a corridor from over 500 years ago and it doesn't have modern day amounts of fire exits! The fire dept realized that this summer and closed it down, much to the dismay of all the visitors that had booked tours in advance.
It has been reopened for about 2 months, then it will close again. Most of the travel agencies offering the tours have made the links not work, given that it was closed -- not sure who or which will offer it again.
For now, if you search for "florence town vasari corridor", it seems to be the only tour agency that is organizing groups..... but since it has been doing that for the last couple of weeks, I am not really sure what they have been doing with the people requesting tours while it has been closed.