DaveReidUK - I am in complete agreement with you that those 15% of new slots are unlikely to be taken up in full by operators for use on domestic flights on a commercial basis. My reference to the comments made by FlyBe allude to this ... see the conditions they set out. Those within the industry can see the obvious flaws in the plan very easily.
The problem is that MP's across regional UK are being sold the line that these flights WILL be coming to their local airport. And that they will supposedly deliver outsized economic benefits to their constituency. And that a PSO mechanism will be used to bring that about. When you write that "nobody seriously expects that to happen" you need to insert "within the aviation industry". Many Westminster MP's are completely convinced that those slots will be filled as promised. Their heads have been filled with this idea, and many appear motivated to cast their vote on the strength of this.
Even on these PPRuNe forums, many posters write with confidence concerning their expectation of new scheduled flights between Heathrow and their local regional airport.
Once the truth dawns, the political votes will have been cast and the funds allocated long before.