Since the new Boarding System dropped (which is neat in concept, but probably needs a little tweaking on the effectiveness of CTA), how do you acquire battleplans from enemy flag ships?
I tried assault actions of all kinds, to no avail.

For me, it works this way -
A successful assault action from any ship transfers a battleplan from the target ship to the source of the assault action.

Example - you lightning strike the enemy ship.
5 seconds later, the assault action is resolved and battleplan is transferred to your vessel.