With the addition of recovery auto registration in the JCA for EAP 5.1 and AS 6.M4, AppServerJDBCXARecovery is no longer required. Indeed its continued use in those server versions may cause premature transaction branch rollback in certain circumstances. In order not to break existing user config files the class should continue to be shipped in the next TS release and then removed in the one after. During the transition period it will be disabled by default, with the option to re-enable by appending ",force=true" to the config string.

see also:
http://community.jboss.org/thread/92291?start=32&tstart=0
http://community.jboss.org/wiki/XARecoveryinJCA
JBAS-8073
JBPAPP-3638