Sky will only fit a line if it suits. They dont like the more difficult connection.
"What if I don’t have a working compatible phone line?
If you are a new Sky TV customer taking Sky Talk Calls and Sky Talk Line Rental, we can arrange for a new phone line to be installed or an existing phone line to be activated (“New Phone Line”). We will confirm the charge (if any) for your New Phone Line at the time of booking.
Sky will not install a New Phone Line where extensive new line construction over and above standard needs is required. "
http://www.sky.com/shop/terms-conditions/talk/Remember in this thread we are talking about a completely new line connection with no strings attached, eg the need to buy an expensive TV Service.
Also we are not talking about starting stopped lines where the full wiring is in situ,and dial tone still exists,which BT and other suppliers will do free of charge, or for a small fee.