It is possible to book one-way AA rewards with IB+, but normally they don't show up. And if the itinerary has stops it can be much cheaper than with BAEC, especially now that the Band 1 redemption cost has gone up.
Take a look at this post of mine from when the increase was announced, showing an example itinerary that was cheaper with IB+:
http://www.flyertalk.com/forum/25629147-post119.html