I solved this retrieving the translations from the entity "Translation Repository" and passing to the Form Model (a model i created to handle the translations):
$nodeRepository = $this->getDoctrine()->getRepository('AcmeCoreBundle:Node');
$node = $repository->find($id);
$translationsRepository = $this->getDoctrine()>getRepository('Acme\CoreBundle\Entity\NodeTranslation');
// retrieving the translations for the given node
$translations = $repository->findTranslations($node);
$model = new TranslatableModel($node, $translations, ...);
I hope this would help someone...
Ciao