Beginning with Tableau 9, any user with access to a view on Tableau Server is also able to see refresh schedules, subscriptions, and other info. Currently there's no way to deny access to this info without denying access to the entire workbook. I would create an idea in our Ideas forum and encourage others to vote it up.
Wanted to resurrect this one and see if anyone has any further insight? We're running into the same thing on our end: users are able to go into the subscriptions page and see all other user subscriptions - wondering if there is a way to have this set up so that they can only see their subscriptions.