I am not going to argue Guardian's case here, as only posted a link to something that I thought was useful, however looking at the BT Sport's page
I can see this wording under header " Already have BT Broadband?" - BT customers with the Sky Digital Satellite Platform. Just add BT Sport to the Sky Digital Satellite Platform for FREE. This will start a new 12-month contract of your current BT Broadband package.
Although it does not say anything similar under "BT Broadband customers", the same may still apply. It would be very controversial to apply different conditions to existing customers depending on how they can/want access BT sport.
Edited by alext05 (Sat 11-May-13 19:35:00)