Yes, the bridge for the spacer pedestal can have a BTA attachment added.
You have fore/aft adjustment by choosing which of the squares locks into the hole on the bridge:


This is the same BTA mount that fits on the J5 bridge.
I realise that the instructions for the AU are sparse and that this sort of info should be covered, I shall be taking charge of improving the information for the bar.

The downside of any integrated bar is less flexibility compared to a modular setup. However, the AU narrows the differential to the point that there isn't a practical downside. The modular bars can get the pads slightly wider but we're talking 27 vs 29 cm so it's special case territory anyway. Obviously the cost is a non-trivial factor, but that mostly goes towards speed.