It's just struck me that the WRA announcement effectively blows the whole Davies report (and its 2015 date) to bits. I think we can see that the decision to build a 3rd runway at LHR has been taken and that infrastructure projects are being progressed on that basis.
As if to back this up I just found this map....
http://www.heathrowairport.com/stati...thwest_LHR.pdf
which I'm going to predict will be very close to the actual announcement - after the General Election.