Using typical 4 conductor phone lines for ethernet is a poor to terrible idea. As a worker in the telephone industry, I will tell you that A) most phone wiring in peoples homes are in terrbile shape, often hardly worth using even for voice transfer, B) four conductor lines have NO TWISTS, and as such you will experience an incredible amount of errors (=significantly lower throughput), and C) these wiring configurations in the majority of homes will have some sort of short, open, or some other problem that will prohibit data transfer in such a manner.
Bottom line: existing phone wiring, for all intents and purposes, can NOT move ethernet through your home.