It does work in a non-embedded case for java:global/env prefix used in both, the definition and the persistence.xml value for the <jta-data-source>.
Laird, please file a bug for the embedded case - it fails with the same exception when ran against a pre-existing install with the -shell.jar.
thanks,
-marina
[Message sent by forum member 'mvatkina']
http://forums.java.net/jive/thread.jspa?messageID=396573