Hello James,

If i'm not getting wrong your meaning,
Unfortunately, that was no option to control all the current user subscribe in your blog site.
But you can configure the setting from your backend > Easyblog > Setting > Workflow > Subscriptions > http://screencast.com/t/kSjSIPPhU (for the next new user )
Allow registrations during subscription -> When you enable this, mean when the new user subscription in your blog site also can register an account during the subscription
Allow category subscriptions -> when you enable this, the user can subscribe to the specify category (but this need to manually to subscribe)
Hope this help.