Medical services to undocumented aliens are provided pursuant to "Section 1011, Federal Reimbursement of Emergency Health Services Furnished to Undocumented Aliens" contained in the "Medicare Prescription Drug, Improvement and Modernization Act of 2003 (Pub. L. 108-173) (MMA)".

This program appears to be adminstered by TrailBlazer Health Enterprises LLC under contract with the Centers for Medicare and Medicaid Services. 

See http://www.trailblazerhealth.com/Section_1011/Default.aspx

and http://www.acep.org/practres.aspx?id=37636

Presumably these programs would continue under the "if you've got it now, you won't lose it" principle.