The relationship between WWE and Progress Wrestling continues to develop as WWE is currently assisting with the financial and logistical elements of bringing Progress to New York the week before SummerSlam. WWE is also helping with some of the bureaucratic obstacles that pop up whenever you're bringing in international performers. Progress is very concerned about being seen as having "sold out" to WWE and WWE is aware of the importance of maintaining an illusion of independence.
The template for the relationship right now is the old relationship WWE had with ECW, with the difference being that this time around WWE has made sure that there can be no other suitors if WWE decides they want to acquire the company. While WWE did ultimately end up with ECW, there was the risk of another party coming along despite WWE's years of assistance, so WWE has definitely learned their lesson with the way they've structured their deal with Progress.
At one point, WWE wanted Progress to actually run the same weekend as SummerSlam instead of the week before. There was talk of Progress running the Friday before NXT to create a three day weekend of shows. Ultimately, it was agreed it made more sense to partner Progress up with EVOLVE the week before as both parties felt it was too soon to so closely associate Progress with WWE.