Judging by the render, it seems as if they plan on incorporating Harbour Place and the other building connected to it with the tower:

Baker Street are not involved beyond being brokers, site is privately owned (same party whon owns the front buildings in The Boulevard) and the current design is by shk although quite a few architects have had a stab at itThe billboard up on site isn't very informative. It just has a huge render, the Baker Street Properties website address, and information regarding office space and parking.
I wonder who else is involved.