I do not believe that is supported in jboss-service.xml. If it was supported, it would nest under the DefaultContext tag set for jboss-service.xml. If you configure the log4j.xml for server.log to record DEBUG, you will be able to track the parsing of the Resource tag. You will find there are no rules for dealing with the tag at this time.
Has there been any change in this since the last post?
No, not AFAIK. It does represent a security concern so perhaps has not been considered by the JBoss team. You can try it and see if they have implemented support. Otherwise you might put it down as on the wishlist at the JBoss SourceForge site.
I haven't tried this on 3.2.2 so I cannot confirm for you the status.