I'm working on adding new event types needed in the upcoming 1.2.4 release. I've created a thread in the JBossCache design forum http://jboss.com/index.html?module=bb&op=viewtopic&t=68267 that explains the proposed solution. You input is valuable to the process. Please review the above mentioned thread and provide your feedback.
I can only repeat: your input is appreciated, as we will collect all callbacks and merge them into TreeCacheListener in 1.3. This *will* break existing code, and we want to break it only once !