Those two schools were the best chance they had. Many PSU fans have been disillusioned with the Big10 for various reasons and the extra Sandusky punishment put down by the Big10 made things worse. PSU has always saw themselves as East Coast and The ACC has many East Coast schools.
NW is a small, highly acclaimed, private school who may seem out of place but fit right in with Duke, WF, BC, Pitt, and Miami. NW resides in the third largest DMA in America (Chicago) and located very close to ND.
Taking the state of Pennsylvania would cut off The Big 10 with its new East Coast members, much like taking UMD cut The ACC off from their new New England brethren. Planting a flag with an original member in a large DMA just might have enticed ESPN to start that ACC Network. ESPN just may have encouraged it. That's the rumor.
All of this being said, I really don't think this happened. ESPN is smarter than that. I have to believe the ACC is as well.