There was the thread a couple years ago (2009) talking about this. The authors say that if you break on impact, then you rout away from the facing of the enemy in contact with you. The facing could be different than the facing after the chargers conform in the Manoeuver Phase.There was one game where i had a bg break after impact combat. The opponent had wheeled 45 degrees just prior to impact and insisted I rout in the direction he was facing. When BGs are in contact, "directly away" is a bit harder to interpret.
I play it that a router must turn 90 or 180, if appropriate, so the the distance between the charger (in contact) and the router is maximized. We don't give the router a choice like an evader would have.
Take a look at:
viewtopic.php?f=43&t=9138