No details of the ruling that I have been able to find, but Maryland's motion to dismiss was based on an argument that the North Carolina court lacked jurisdiction and the University has sovereign immunity, so apparently the court rejected both of those arguments.
Note that this does not mean that the ACC has "won" or even that they will win. This just means the case can continue for now.
Note also that immediately after this news was reported, rumors of the Big 10 poaching the ACC again started popping up on Twitter, and it seems like Maryland folks started this batch. Just saying: keep in mind the timing.