Hi Vegas,
Currently, Microsoft Office 365 customers who utilize single sign-on (SSO) through AD FS 2.0 and have multiple top level domains for users' User Principal Name (UPN) suffixes within their organization (for example, @contoso.com or @fabrikam.com) are required to deploy a separate instance of AD FS 2.0 Federation Service for each suffix. There is now a rollup for AD FS 2.0 (http://support.microsoft.com/kb/2607496) that works in conjunction with the “SupportMultipleDomain” switch to enable the AD FS server to support this scenario without requiring additional AD FS 2.0 servers.
Best Regards,
Bruce Zhou