I interpret "application specific xml file" to imply "not in jboss.jcml format".
Yes. Create an mbean for the new XADataSourceLoader, configure its attributes through the mbean server, and call init and start on it, again through the mbean server. Be sure to give it a unique ObjectName. An example of doing something similar for jboss 3 is in a jboss 3 test case, I think org.jboss.test.jmx.test.ConnectionFactoryLoaderUnitTestCase if I remember the name correctly.
Is it possible to do this at deploy time? I would love to be able to specify the Datasource as part of the deployment descriptor as opposed to in the JBoss.Jcml.
use 3.0 and include a sar with the datasource config in its jboss-service.xml. Put the sar in just about anything else, such as ear, or ejb-jar and the datasource will get set up before the rest of your app. It's easier to move to 3 than explain how to do this in 2.4.x
Could you please kindly post an example of this DS configuration in the service.xml of a sar file for 3.2.0RC1?