From the Wiley press release:
This agreement, which marks Wiley’s first in Latin America, positions UNAM as the leader and pioneer in the development of open access research, allowing its researchers to publish most if not all of its articles open access across Wiley’s portfolio of hybrid journals.
It's a strangely spare announcement, with ambiguous language ("most if not all," hybrid journals only?). Without more details, the "deal" looks like a PR stunt: Latin America—home to the nonprofit, fee-free alternative—joins the read-and-publish club.