find | grep mce returns [installpath]/wp-include/js/tinymce/…
[installpath]/wp-content/plugins/…
I guess what I find this way is the JavaScript hooks
same search with MCE in capitals returns only references to the TinyMCE Comment plugin.
Search for api or API returns nothing.
Software changes from 2.3 to 2.5 is unknown to me, I used older versions of WP until I upgraded to 2.5 (svn)