The only ones who win are the big business guys and gals. The American worker loses due to lower wages and lack of work. The American taxpayer loses due to increased costs for schools, roads, etc. The illegal workers lose since they are paid sub-standard wages, receive no benefits, and have zero rights.
The Camp of the Saints is a great book about what might happen if say 500 million Chinese show up on the Western coast of the United States demanding entry. If Mexico gets this deal, how long before other countries demand equal access?