Thanks for the clear answer ;-)
You should be able to, just not to the jbossesb-server.
The jbossesb-server profile does not support EAR deployers nor EJB.
It seems the question was not how to deploy the whole ESB as an EAR but to deploy a .esb archive in a .ear.
While that is untested at this present time it might work. Much like you can deploy a .war in a .ear, a .esb archive works in a similiar way.
Please experiment and tell us what you find.
This should be no different from deploying any other jboss artifact in an ear.
The deployable artifact must be listed in the application.xml or jboss-app.xml as a module so that the EAR deployer will pick it up.