I'm using JBoss AS 4.2.2.GA and the JSF implementation going along with it. When I tried to inject a session bean to a JSF-managed bean (i.e. this bean is declared in faces-config.xml), I got the exception Injection failed on managed bean. javax.naming.NameNotFoundException ... (not sure if I did anything wrong, I can give you the source code and the EAR file if it is needed).
The example application JSF - EJB3 I downloaded at http://www.redhat.com/docs/en-US/JBoss_Enterprise_Application_Platform/ doesn't use @EJB but uses JNDI lookup. That makes me doubt that @EJB can be used in JBossAS 4.2.2.GA.
Your assumption is correct - @EJB is not available in 4.2.x. You will have to wait for 5.0 to use that. Essentially, the "server" portions of EJB3 are available in 4.2.x, but not the "client" portions.