Oh snap! Blair wouldn't go to City Hall for that. Police pressers are held at their HQ. He won't be there to arrest Ford personally but I wouldn't be surprised if he is giving the Mayor the courtesy of a personal heads up: "My officers will be here in 1 hour to pick you up, please get yourself presentable and prepare your things".
This is the timetable I discussed some pages back. The police have to act before the Lisi documents are released to the public. If there's something incriminating in there -- even as small as buying drugs -- then the public will rightly demand answers as to why Ford hasn't been charged and suggest that the police are giving him preferred treatment, even though they may be waiting on something bigger. If Ford isn't taken in for questioning or if no Bill Blair statement is given today or tomorrow before the documents are released, then there is nothing incriminating Ford in them (which has strongly been suggested by several parties that is not the case. This is about Ford, he's in the Lisi ITO docs).