Newbie question – What happens with registered users?

Hey community!

First of all before you throw an egg on me head, I searched throug out the forum for an answer. Although I found many answers and possible solution for my problem, I had to ask my question here.

As a non-profit organization we have 16 locations. I understand WordPress Network makes it possible for end-users to create an own website with their own plug-ins and content (I hope I understood right). Under a main domain, we want to have sub-domains for each location to create their own website with their own contents and plug-ins. Is this possible with WordPress Network?

There is a one important thing which is a must. We want to share data of registered users. This means that when someone is registering (on the website for an account), the head quarter is also receiving the subscription. Is this possible?

If not how we can do this?