Yes you need the Premium version to use the Social button / function.
But even then I doubt you could exchange work space / work plan as you describe in your OP.
Reason I say above is that we cannot even export a work space and then import the same work space to our own Accounts so I very much doubt you could send to a friend for him to import to his Platform.
You could chat and send an .itf file or a screen shot of a Chart to a friend using the Social button (On Premium) but not send work plans / work spaces to friends.
I stand to be corrected by anybody who know better?