In addition to Guffa's answer, you could use this variant to have a more shorthanded notation.
public static bool ScrambledEquals<T>(this IEnumerable<T> list1, IEnumerable<T> list2)
{
var deletedItems = list1.Except(list2).Any();
var newItems = list2.Except(list1).Any();
return !newItems && !deletedItems;
}