Join Date: Aug 2011
Location: Barcelona, London, on a plane
Programs: IB+ Gold, TK E+, Hyatt Globalist, Marriott LTP, IHG Diamond
Posts: 14,182
Presumably you mean booking a flight on IB metal as an AA codeshare.
Until 24 hours pre-departure, you would deal with AA for ticketing issues. However, IT glitches may mean that you won't be able to select seats, etc.
Personally, I would avoid codeshares unless you are saving a lot of money.