I'm not sure about ADFS, but SAML is an XML based data format, so there are plenty of options for either getting XML data into FileMaker or outputting XML data from FileMaker. It really depends on the details of what you want to do. Either way FileMaker can work with XML data.
Were you able to determine if these are supported?
No, FMS does not support Federated Services. But you can certainly establish a trust between two domains and have users authenticate across domains. This was tested and verified way back when FM7 was released.
Could you reference any material on establishing trust between two domains and authenticating accross them?
Thank you! I'm not sure if this will work for my application, but I will look into it.