My understanding was that BAA were seeking consent for mixed mode operation coupled with an increase in total permitted movements. Perhaps consent for the former should be given, but not the latter, thus creating a surplus in capacity which would be available to shorten delays caused by weather, blown tyres or even self important visiting heads of state?
There may well be extra costs involved - ATC manning for example - but they are miniscule compared to the costs incurred by airlines and pax from disruption.
Hey BAA - make a big contribution to customer service!