Transfer at T2
As T2 isn't fully operational yet, no one can fully advise you on the process of transferring, especially with regard to time taken to clear US customs and immigration. But I CAN tell you that transfers within T2 require you to be re-screened. Not sure however if EI Regional flights will use T2. Maybe once EI move their USA operations over you might consider asking again as people will have experienced the transfer process.