Dan, did you have any luck with configuring Shibboleth for multisite? You might check out this patch, if not:
https://www.ibiblio.org/archive/2011/10/wordpress-multisite-plus-shibboleth/
We’ve long had a goal to get Shib working with two large domain-based multisite networks. Using the patch above worked, but ultimately we still had conflicts with the Shibboleth and Domain Mapping plugins (for *domain.edu sites) and that sent us back to AD/LDAP.
Would love to know if you’re successfully using Shib for your netowork.
