I will check again the contents of freepbx.log to see if it delivers the detail that is being requested, which is basically tracking of configuration changes. (For example, if someone changed a trunk configuration, which trunk was it, and if possible, what fields of the trunk config).
I know this is a complex feature from a developer’s perspective. Now I’ve found this thread http://www.freepbx.org/forum/freepbx/users/freepbx-log and it explains that the level of tracking detail I’m talking about is not possible today.