It looks like the answer is 2:00 p.m. Eastern.
DC Comics plan to implement day-and-date synchronization for their comics digitally and in print is still set to begin today. Alas, I just checked comiXology, and it doesn’t look like iPads are going to be competing with any of the midnight release parties going on around the country right now.
The DC Comics app itself (which is basically just another storefront for comiXology) currently shows no sign of Justice League #1, but DC section on the main app does appear to have some redesigned heroes peeing out. The box on the Featured page, meanwhile, clearly indicates that the new Geoff Johns/Jim Lee-made Justice League #1 will be out in about 12 hours.
I wonder if this is going to be typical roll-out model going forward. I don’t recall reading any interviews that articulated 2:00 p.m. release time. If you have, though, I’d very much like to see it.
Anyway, it looks like this book is going to be a paper buy tomorrow.