Google Play Music had a special playlist called "Shared with me", but it's no longer available. The playlist included all the songs shared with you by Google+ users.
Here's how Google described this feature: "Share a free play of the songs and albums you've purchased on Google Play with your friends on Google+. They can share their purchases with you too. Forget the name of that song shared with you last week? No problem, you can find all of the music shared with you in your 'Shared with me' auto playlist."
The auto playlists section from the sidebar only has 4 auto playlists: "queue", "thumbs up", "last added" and "free and purchased".
{ Thanks, Boris Larson. }
