Those organizations are "H-1B cap-exempt" organizations that are not subject to the annual H-1B lottery. Cap-exempt organizations include non-profit institutes of higher education, organizations affiliated with these institutes (like hospitals), non-profits primarily engaged in research, and government research organizations, like Fermilab and NASA. If you get a cap-exempt H-1B, you could transfer to another cap-exempt organization but you would not be able to transfer to a cap-subject private for-profit entity although you could get approved for part-time concurrent employment with such an entity.