Yes it can be ealiy deployed to server/default/deploy folder
however there are couple of requisites:
1. Check if the jbpm-{dbName}-ds.xml file is present in {server.home}\server\default\deploy\jbpm folder or {server.home}\server\default\deploy
2. When the jbossAS is booting up search for the name JbpmDS. (ctrl-f) in the ApplicationServer logs. it will tell you the name to which the datasource bound to . It is assigned to java:JbpmDS (without the /) in my case.
3. Open up jmx console @ localhost:8080 and look up for the datasource bindings. Enable the jbpmDS if it is not previously enabled.