You have to have a Sky telephone line for Sky FTTC correct. The voice side of the line isn't touched by the FTTC.
The data side goes through the Openreach DSLAM and onto Fibre and at the exchange the fibre is interfaced to the Sky Broadband equipment.
pro (16.8/1.2) - Ordered Sky Fibre Pro 45.6/6.5 - 4th sept
13 years of broadband - ntl:cablemodem/BTbusiness/metronet/bulldog/BE/Sky