If the new owners of Edinburgh wanted to cause BAA some (more) pain at Glasgow a competing operation on the west coast would do just that and as Prestwick competes directly with Glasgow it may become an attractive proposition for Edinburghs owners.
It's hard enough to make money taking on a new airport without taking on a different airport with a wholly different ethos and business model just to **** off a competitor. It's not the case that Scottish aviation is so lucrative that gold bricks are common place, just ask Infratil ! Unless there is a benefit to shareholders in taking on a loss making PIK operation, it's a fantasy. There are synergies between EDI and GLA, some that hold one or both back arguably, but I can see no cost benefit or synergy between PIK and EDI.