Resolution:
Like Administrator, XML Canon uses the web server Tomcat. Thus, by following the procedure outlined in Chapter 3 “Installation on UNIX Systems” under the section titled “Configuring TIBCO Applications to Run in 64-bit Mode” and specifically under the subsection titled “Modifying Administration Server for Solaris 10, 9, and 8 on SPARC” and well as modifying xmlcanon.tra file to point to JRE 1.5.x.

Here are the instructions modified for XML Canon files:
1. cp $TIBCO_HOME/tra/5.5/wrap64 $TIBCO_HOME/xmlcanon/xmlcanon/3.1/tomcat/bin/xmlcanon64
2. cp $TIBCO_HOME/xmlcanon/xmlcanon/3.1/tomcat/bin/xmlcanon.tra $TIBCO_HOME/xmlcanon/xmlcanon/3.1/tomcat/bin/xmlcanon64.tra
3. cp $TIBCO_HOME/xmlcanon/xmlcanon/3.1/tomcat/bin/xmlcanon.sh $TIBCO_HOME/xmlcanon/xmlcanon/3.1/tomcat/bin/xmlcanon64.sh
4. use JRE 1.5.x and sparcv9 in xmlcanon64.tra
5. use JRE 1.5.x and sparcv9 in xmlcanon64.sh
6. use the new "xmlcanon64" wrapper in xmlcanon64.sh instead of xmlcanon.sh
7. launch the XML Canon server with xmlcanon64.sh.

(Note: The credit goes to Matteo Picciau for taking the initiative on this one.)

How can I enable XML Canon 3.1.x to run in 64-bit mode on 64-bit Solaris under JRE 1.5.x that ships with TRA 5.5.x?