Yes.
Atlassian Crowd and EasySSO do work together, but only if Atlassian Crowd is used as a user directory in the backend.
If (before you discovered the magic of EasySSO!) Atlassian Crowd was used for single sign-on then the Atlassian Crowd SSO configuration MAY interfere with EasySSO.
EasySSO performs authentication “before” the request reaches the core application (JIRA or Confluence).
Once authentication has been performed and the user is identified, by IOPLEX Jespa library communicating with Domain Controller, the username is handed over the Application in the same way as the default authenticator does. Atlassian Crowd in this scenario plays a role of a back-end user directory and is not involved in the authentication process.
Currently for external Crowd directories there is a limitation that the user must exist in the application already (i.e. synchronized) before EasySSO can perform auto-login. This limitation doesn't exist for LDAP-based directories e.g. Active Directory.