Robinson revealed further E2 details and hints in a podcast on Comic Vine last week. I dunno if any of this stuff has been posted yet, but anyway, here goes-
-Robinson has stated that the final strength of the Justice Society in his book will be 'more than five' members.
-Ted Grant/Wildcat will eventually be a major player in the book.
-There is a new character, an Amazon, who will join the team and some point and seek to avenge Wonder Woman's death at Steppenwolf's hands.
-Hawkgirl is exclusive to Earth 2; in a similar vein, as per an editorial mandate, there will be no direct doppelganger's between Earth 2 and Earth 0 (which is one of the reasons why the Trinity were killed off).
-E2 is apparently a more 'metaphysical' world, with many of the heroes' origins/powers having a mystical aspect (including the seemingly scientific origins of Atom).
-While the book with focus on the Justice Society, there will also be some focus on the larger universe and other characters not directly connected to the team.
-Helena's mother IS Catwoman, and at this point, Robinson is unsure as to whether or not she's still alive and/or will be making an appearance.
-Robinson won't necessarily be employing plot details from the original pre-Crisis Earth 2.
-There will be flashbacks to the era of the Trinity.
-Superman, Batman and Wonder Woman were the first heroes of E2; and they began their careers around '9 years ago' (though Robinson wasn't too clear on that).