> From which sibling would the new scope of the child element controller
inherit?

Not sure I understand the question.

If you have this:

```
<div ng-controller="Ctrl">
  <div ga-map>
    <div ga-context-menu></div>
  </div>
</div>
```

And if the map directive has transclude:true then the parent scope of the ga-context-menu element might be that of Ctrl. I'm not fully sure because the map directive doesn't have a template and doesn't use ng-transclude. But I would have liked to give that a try :)