XJC: migrating ant task from JAXB to JDK 1.6 - ant

Question

We have migrated to Java 1.6 and as part of the there is a re-write of the ant tasks that used the older xjc ant task to use the executable: xjc.exe provided in Java 1.6
We also need to retain older ant task parameters like using commons-lang plugin to generate toString() methods in the generated value objects.
Earlier:
<target name="generate_vos" description="Compile all Java source files">
<echo message="Compiling the schema..." />
<taskdef name="xjc" classname="com.sun.tools.xjc.XJCTask">
<classpath refid="ERPSimulator.classpath"/>
</taskdef>
<delete dir="${jaxb.src}" />
<mkdir dir="${jaxb.src}" />
<xjc schema="${jaxb.schema}/SOAPClientObjects.xsd" package="xxx.jaxb.vo" destdir="${jaxb.src}">
<arg value="-Xcommons-lang" />
<arg value="-Xcommons-lang:ToStringStyle=SIMPLE_STYLE" />
<produces dir="${jaxb.src}" includes="**/*.java" />
</xjc>
</target>
Now:
<target name="generate_vos" description="Compile all Java source files">
<delete dir="${jaxb.src}" />
<mkdir dir="${jaxb.src}" />
<echo message="Compiling the schema..." />
<exec executable="xjc">
<arg value="-extension"/>
<arg value="-d"/>
<arg value="${jaxb.src}"/>
<arg value="-p"/>
<arg value="xxxx.jaxb.vo"/>
<arg value="${jaxb.schema}/SOAPClientObjects.xsd"/>
<arg value="-Xcommons-lang"/>
<arg value="-Xcommons-lang:ToStringStyle=SIMPLE_STYLE" />
</exec>
</target>
However, running the new task results in errors as the -Xcommons* plugins are not carried forward in this version.
I have explicitly set the plugin jar files for the commons-lang toString plugin in the path too with no luck.
Any idea how to make XJC.exe generate the toString() method for the resultant Objects?
Thanks!