In RTW: Barbarian Invasion, I killed an entire Western Roman army in a non-town battle, including at least one unit of Legionary First Cohort. Definitely saw that eagle and made a point to wipe that unit out to a man.

Had a faction member as general. But I didn't get "the A Roman Eagle" message card after the battle, nor did my faction member's info details indicate anywhere that he was an Eagle Taker.

I've had this happen a few times, both in and out of towns where sometimes killing these cohorts gives me the Eagle, sometimes not. Are there some conditions I'm not meeting or what's going on? Is it just random?