MEWA sponsoring organization has insured health care benefit covering its own employees and those of many other employers but only receives and processes information regarding eligibility, what would be its HIPAA obligations?

I am not clear as to whom you are referring? By "its" are you referring to the sponsoring organization as a participating employer, or to the MEWA itself (which should have very very few employees eligible for the benefits? In fact what do you mean by "sponsoring organization"?