Ignore the date being changed to December.
Basically. every quarter, the BT wholesale checker simply moves dates on by 3 months if the particular cabinet is not yet live. Once the cab is close to being RFS the date will be amended to a closer, more acurate date rather than they default 31st December.
So basically, because the cab wont be ready in time for 30th September, they just move the date 3 months automatically. This doesn't mean the cabinet deployment has been delayed, just that they are working on a 3month turnaround.
Naturally dates that keep moving back for months on end may have a particular issue as to why that cabinet isn't RFS yet.