On PCs... if there is a folder named ' Plugins' inside the special subfolder C:\ProgramData\SketchUp\SketchUp 2014 then that is added to the $: [aka $LOAD_PATH] and then as SketchUp starts its contents [if any] are auto-loaded for ANY user... However, the AutoInstall tool of SketchUp will always use the User's own 'Roaming' Plugins folder! BUT using the AutoInstaller in the SketchUcation PluginsStore's dialog [or its Archive Installer menu item] will see that additional folder and prompt you to select the main Plugins folder OR that 'shared-folder' as the installation's destination - thus allowing an AutoInstall into any selected folder...