This has been a strange definitions battle for years where opponents of charters have tried to label them as private entities and charter advocates keep emphasizing that they are public. It's particularly strange, however, when a charter organization lobbies for the label of private. In 2013 there was an amicus brief filed by the California Charter Schools Association stating that "nonprofit operators of charter schools are 'private' entities and not a public entity" (p. 9). It was apparently being used to allow certain policies to stay in place. The issue is: you can't have it both ways in accordance with the law.
So, this most recent determination has short-term and long-term outcomes. Short-term it means that employees wishing to unionize will do so under the National Labor Relations Act instead of under state laws (as public employees would). Long-term, it might erode some of the standing that larger networks have when they try to label themselves incorrectly.
I'm really curious to see where this will lead.