I know it is possible to have a Seam managed EntityManager. However it is not possible to set the persistence context for it using the usual JPA annotation. Instead, the persistence unit is set in the the Seam components XML file.
This is all fine if you only have one persistence-unit, what happens if there is more than one persistence unit and you require some of POJO's to use one EntityManager with one specific persistence unit and some of your other POJOs to use another EntityManager talking to another persistence unit?
Can this be done?
This really has nothing to do with Seam (its easy to inject SMPCs which reference different persistence units) but to do with binding the entities to the correct PU. Ask in the Hibernate JPA forum.