Actually they havent "waived it through" to the EC. The primary jurisdiction is with the EC in a case like this due to turnover in other jurisdictions than the UK. It is quite unusual for the OFT to run a parallel case when the EC has jurisdiction, and as they say, they will be providing input to the EC to assist the consideration of the case.
As to whether it will get delayed further, the EC doesnt give a damn about what the parties think about the need for speed...they will take as long as they think it needs to resolve any competition issues on specific routes, and willl drag it out if they think that is necessary. They were very close to dragging out the takeover of bmi by LH in 2009 over one route that had less than 20k pax a year. There are much more significant issues with this deal.