It is a strange thing to do -especially as they still have completions going on and new people therefore finding new problems (maybe us for one!) As you say it leaves alot of space in that building- they have other plans for it maybe
It did cross my mind that they hope the distance will put people off making noises about minor concerns. Except that when its your property it wont seem minor. Maybe they are downsizing again- or feel that a call centre is all thats needed. If you go to CdA without your own transport it will be very difficult to visit Balsicas.
However, I understand that in the early days they were just based at Balsicas and people just had to phone in about problems or take the time to go and visit them. So it has been managed like that before.