My suggestion is to put your data into /usr/share/tomcat6/conf/context.xml which is a symlink to /etc/tomcat6/context.xml on CentOS 6. At least tomcat6 does read the contents of that file when it restarts, and I had some luck getting resource data loaded from there. It would seem that this file is new in tomcat6.
I used strace to check which files it was visiting and it does run stat() on the various files like /var/lib/tomcat6/webapps/*/META-INF/context.xml but nowhere does it actually open() those files, so I'm pretty sure it does not read the contents. Maybe some bug? Maybe imaginary future feature?
I managed to get Plandora (uses context to supply MySQL database connection details) running on CentOS 6 with these packages (from yum):
apache-tomcat-apis-0.1-1.el6.noarch
java-1.6.0-openjdk-1.6.0.0-1.61.1.11.11.el6_4.i686
mysql-connector-java-5.1.17-6.el6.noarch
tomcat6-6.0.24-52.el6_4.noarch
tomcat6-servlet-2.5-api-6.0.24-52.el6_4.noarch
tomcat6-el-2.1-api-6.0.24-52.el6_4.noarch
tomcat6-admin-webapps-6.0.24-52.el6_4.noarch
tomcat6-jsp-2.1-api-6.0.24-52.el6_4.noarch
tomcat6-lib-6.0.24-52.el6_4.noarch
tomcat6-webapps-6.0.24-52.el6_4.noarch
Just in case anyone else is trying to get Plandora to work on CentOS 6, you also need to make sure you symlink:
ln -s /usr/share/java/mysql-connector-java.jar /usr/share/tomcat6/lib/