It is possible to configure single sign on in Service Catalog 14.1 in an environment that has multiple ADs.
My environemnt uses EEM pointing to varios AD servers, and these AD servers are from different clients (different domains).
Are the Active Directories trusted ??
If yes you can use the following link to configure the single sign on
Integrate CA Single Sign-On with CA Service Catalog - CA Service Management - 14.1 - CA Technologies Documentation
No, ADs are not trusted
If the AD's are not trusted then you can choose the Multiple Microsoft Active Directory Domains in the Configuration Type in the Directory Information for the user store in EEM
Please let me know if you have any further questions