According to an interview with Mike Marts
, "Yes, it all takes place within Gotham. The one exception is the one issue which actually takes place in the past, which is All-Star Western. That chapter takes place in New Orleans." .. and ..
"we've hinted that their reach goes back into the history of Gotham City. So it's conceivable that they could have been around 100 years ago, during the time of Jonah Hex."
He also claims that since they are re-animated, some of the Talons we will see fighting the Bat-family may be from different time-periods.