The towpath closures have started, but the path is being kept open as much as possible. I had a chat with the rangers and one of the workmen this morning. I got through OK today, apparently tomorrow (Tues. 28th) it'll be shut. Diversion posted via Station Rd and the footpath to Dixon's Lock. Look for a yellow arrow. The main problem is at the Dixons end heading north, the arrow is up but you won't actually know if the path is closed until within about 50 yards of the road at the other end.
update
From a chat with the workmen this morning.
The footings trenches are about to be extended towards the towpath, so the path will be shut off for the duration, probably starting tomorrow, Tuesday 05/10/2010. Diversion as expected from Dixons Lock via footpath to the Hollingwood Centre, turn left onto Station Road, left onto Troughbrook Road and rejoin towpath by Hollingwood Lock. (and vice versa).