What happened is that you don't get advantage anymore when attacking from behind (thank goodness). You still get advantage from highground, so ranged sneak attack should work just fine, unless advantage is cancelled out (long range, enemy hidden in shadows etc.)
You can still gain advantage when attacking from shadows, but sneak attack also triggers now, when enemy is engaged by one of your companions. So you enemy A is standing close to your companion (or someone hostile to him) you should be able to sneak attack him - a word of warning I did find this to be a bit unreliable at the moment, with sneak attack still not being possible, even though there is someone standing right next to him.
