My guess is UA had a heads up on this before everything went public. Remember the remaining airline is US, if the deal goes through. UA is weak in the southeast and to the islands and US provides a lot of support for UA. Otherwise, they may lose revenue to DL or AA.

While US would still be *A, the code-shares mays it looks like UA is operating flights in areas that it is weakest.

In addition, both US and HP is weakest in the midwest where UA has strength.
The catch is Air Wisconsin has a lot of gates at ORD and the will no longer serve as UAX.