Single Sign On Implementation

We are getting ready to implement Single Sign On (SSO) for EPBC and PCMCS.   Both EPBC and PCMCS are currently in production with user names that do not meet corporate standards and will be changed to comply prior to switching to SSO.  We successfully ran the SSO test from the SSO Configuration tab of the Cloud My Services Users page, but are not able to test the functionality of EPBC or PCMCS (executing the SSO test simply returns an Authentication Successful message).  Is there any fall back once we turn on SSO?  If we have issues, are we able to