In an IDE environment, you want to know what will be generated by a plugin without having it execute. For example, if you have a plugin that generates a source directory you want to know that without having actually execute the plugin because it can take a long time if you have a lot of plugins.
Another issue will probably have to be created to outline changes to the plugin api so that external tools can call this method to get all the information up-front. I couldn't find any related issues.
This should also work when reactor projects are run.
Another example is any plugin that produces resources that need to be added to the UI.