Normally, we do back ochos in crossed system - the lead changes his weight - so lead and follow are right/right & left/left in terms of their foot placement. In parallel system - the normal walk is right/left & left/right - in terms of which foot/leg we are stepping with. (This basic primer is for the beginner/readers.)
It is possible to do back ochos in parallel - essentially the leader is doing a front ocho to her back ocho - stepping with the right to her right (outside) and then pivoting and stepping with the left to her left (outside).
The key for the lead is not to change weight - at the moment when you lead her into the first back ocho (to your left) - step across (in parallel system) with your left - placing your foot on her left side - then as you lead the next ocho - you pivot on your right foot and step across with your left foot.
I had forgotten this. It's kinda cool. Try it.
I didn't really try it in close embrace. Our students here have been dancing salon/open for the past year. We're going to have to gradually introduce them to milonguero/close embrace.
I think it's possible in close embrace, but with a very fluid/dynamic embrace. I'll have to give a try.