1) Static ip's are assigned to your Network Login ID which you should have entered for the hub settings when you run the setup disc for the broadband setup/install (it will look like this; Username: B123456@hg30.btclick.com - Password: ********) If entered correctly your fixed IP address.
2) Do the cameras connect to some kind of a server device or control unit, which then connects to the hub? If so then yes it can be done, providing your camera control unit has this feature.
3) Not 100% sure on what your asking here, but I'll have a go. Port forwarding isn't always necessary, it depends, some CCTV control units have software included that you can install on a PC/Smartphone where you create a login and can stream live without forwarding router ports. If it does need port forwarding you will find you can connect to the camera on the same internet connection but anywhere else fails, this is the hubs firewall/security doing it's job and preventing an unauthorised and potentially harmful incoming connection, this is why the router can be set to open certain ports to allow an authorised incoming connection only to ported device. If your not confident port forwarding the router, call BT Business Support, they will do this for you (providing you can tell them which port numbers need opening, for this refer to Camera instructions or Manufacturer support).
4) Think I covered this question on question 3?
5) How do I enter my broadband network username and password on the Hub 3?
How do I set up port forwarding on the BT Business Hub 3?
6) Do they connect to a unit?
Hope it helps 
