You can only tell if someone views the profiles, and all you see is the number of views. For instance, on your own profile, I see "This page has been accessed 32 times."
On open profiles, you will see a G+ symbol, and if that is clicked, the profile can be shared on Google+. I believe you see numbers tick up if that is shared. If someone merely shares the profile in an email or text, you will not see that, but the number of page views will increase.
As far as the sharing on Facebook option, I don't know if you can tell if someone shares that. In any case, if the profiles are private, they won't be viewed.
