Hmm, would have thought some building work would have started by now. Then again I have also heard that the Banbury resignalling has been put back as well.
This post in the ongoing Banbury works thread mentioned groundworks going on in the former depot back in late November:
http://www.railforums.co.uk/showpost.php?p=2376531&postcount=81
Signalling is due to be done in the first week in August, it was announced by NR recently and I linked to their PR piece in that thread.