Uh, I've probably been totally unclear. By global setting I meant Defaults/Base File.sublime-settings and User/Base File.sublime-settings. By plugin (local) setting I meant something, which is present in MyPlugin/MyPlugin.sublime-settings and User/MyPlugin.sublime-settings.
The thing why I ask this, is that I have a plugin with a whole bunch of defaults. When an end-user wants to customize it, he/she creates a corresponding file in User/ directory and overrides separate settings, as usual. I want to reference one of these settings in keymap, but, as far as I see, I can only use something from Defaults(or User)/Base File.sublime-settings, but not MyPlugin(or User)/MyPlugin.sublime-settings. In this case, end-user would have to edit both User/Base File.sublime-settings and User/MyPlugin.sublime-settings to fully customize the plugin.