Getting tickets earlier than on Ticketmaster?

Rumour has it that a chunk of U2 tickets were sold out long before they were launched this morn on Ticketmaster. Were they bought by fans who subscribe to the fan club or how would one go about getting on some kind of list or other way of getting tickets made available early? I know if your phone is with 3, you can sometimes get early access to events in the 3 Arena. But what about for say U2 or when (as rumour has it) Ed Sheehan plays Croke Pk? Thanks