Would he not contact the ESB, and ask them ? That way he will have the correct information.
It sounds like your friend has been conned. That said, he nearly deserved it, how could he be so silly as to do nothing for 8 months ?
He needs to get the correct information, and armed with this, demand his deposit, and a refund (if he has actually paid for the ESB next door), from the landlord. Let them know that he will have to get the Guards, and the Rental Board, - and maybe mention Revenue - involved, if he refuses.
No good going to the landlord with bits of information you got on the 'net and vague queries - he'll never get his money back otherwise.