First, my understanding of how digital and analog cable works:
Analog cable uses a copper wire to simulate regular airwaves. TV channels are sent as plain old RF signals. PPV channels are scrambled, and the cable box (about the size of a small phonebook) descrambles them. I never did figure out how the cable co. authorizes a PPV channel for a particular box.
Digital cable uses data packets transmitted on a low frequency RF signal over a regular copper wire, or in some places, as a pure digital signal over fiber. Instead of each channel being an RF signal, they are digital video streams. The channel numbers have nothing to do with frequencies. Infrastructures capable of digital cable TV are also capable of carrying TCP/IP packets, which is how cable internet service works.
I am probably waaaaaaaaaayyy off on the digital cable description, but why does it matter?
Second, about the phone line requirement. I have Charter digital cable. They give customers a Motorola DCT box, which is about the size of a DVD player. It doesn't use a phone line, but instead retrieves TV listings over the cable network. PPV ordering is also done over the cable line, but premium channels must be ordered by phone.
Again, I have no idea what I'm talking about. I worked at a cable TV station once and learned quite a bit about the workings of analog cable, but I know nothing of digital cable.