I have the following query working which gets the results I want:
int associatedId = 123; MyObject alias = null; var subQuery = QueryOver.Of
You cannot do that using QueryOver, Criteria or Linq. The only way you can do this is via HQL.
http://www.codewrecks.com/blog/index.php/2009/09/04/theta-join-in-hql-join-with-unrelated-entities/