Thanks for the link. For anyone interested, here's the process outlined in the document, I'm gonna try to apply and see where that leads.

# Steps to interoperate with Messenger or WhatsApp

Note: Separate documentation and applications are required for Messenger and/or WhatsApp

    Review: Review the Reference Offer, Developer Documentation Overview, and Application Guidelines above.
    Apply: If you believe you qualify, complete the form that’s linked in the Application Guidelines.
    Review: If you meet eligibility requirements, we will send you our detailed Developer Documentation under NDA for review of the detailed technical requirements for interoperating.
    Sign: If you can fulfill the relevant terms and technical requirements set out in the Reference Offer and want to request interoperability, sign the Interoperability Agreement that we will provide to you.
    Build: Start building interoperability.
    Enable: Complete the milestones outlined in the detailed Developer Documentation to enable interoperability.
    Launch: Work with Messenger and/or WhatsApp on a joint plan to launch interoperability.