Carr peaked in the home 1-1 game VS Portugal in 2001, basically holding off the opposition with Keane in imperious form in central midfield.
Since then injuries have taken a toll on the former Premiership full back of the season. Along with Finnan, he's the only regular starter in that position this season (O'Shea has played there, at centre half) but with previous retirements may have blotted his copybook with the FAI, if not the current regime.
Finnan and Kiely only agreed to return after speaking to Trapattoni, but Carr had retired completely from the game at the time. His return with Birmingham was only supposed to be temporary, but here he is nine months later back playing in the Premiership and not playing badly either.
I'd imagine it would take a call from the management to see if he's interested in returning, and I doubt he would call them spontaneously to declare his availability.