1) UAL has opitions (If you think UA isn't behind this idea your nuts)
2) Nothing is ever as clear as you think it is when the news first gets out. This LCC idea of ACA's was half baked from the moment they announced it. Many stations they list as assets on thier route network are owned by UA, not ACA. Example. ABE employee are not ACA with right to return to UA, ABE property is still LEASED BY UAL not ACA. Same with CAE, CHS, and many others. This does not include ACA stations where UA operated flights and is staffed by UA employees like PHL, PIT, JFK and others. Bottomline ACA isn't as big as it seems when all those stations are given back to UAL. Then ACA woudl have to lease thier own space and hire its own employees or contract out.
It seems now that ACA not UA painted itself into a corner. Mesa is offering a way out. They have the means to do it.