My Sky installation Engineer connected me up with a Phone Line which I have left unconnected. As ChuckFickens says, you do not get interactive services but it is not a problem, and if I decide to connect it to Telephone socket in future then I can do so.
If I wish to upgrade or downgrade Sky services in the future then I can do so on Line or over the Phone.
Sky would like everyone connected up to Phone Line as they will then try and sell you their Broadband Package, but I am quite happy with BT at present.