ATVocabulary Manager with MasterSelectWidget

I am using MasterSelectWidget in one of my projects to create the master-slave/master-slave combo of select widgets in my form It then occured to me how nice would it be if I could get my vocabulary from ATVocabularyManager which I have already installed on my site. Well, I lied it's not actually nice... it's one of the requirements :). Anyway I tried a few times to point my dynamic vocabulary at ATVocab's method but it failed to load up the Select widget with it's values. I wonder if this has been done by anyone ...