I'm not aware of a way to get this.
In the analytic tool we can see who has a "watch" on a community. You maybe able to see who is watching a person.
We did a customization that would show you the number of people for e-mail subscriptions on a per-content basis at save/publish time.
So, for example, if I edit a blog post, right above the Publish button, I can see how many people will get an e-mail:
If I click the "18 people" link, I can see the names. Likewise for creating or editing either a document or a blog post. It shows all the people who:
are notified due to the author
are notified due to the container
are notified due to the content
It's nice to know who will see your changes via an immediate e-mail.