Complex sentence: NESN was, for a time, the New England carrier for Fox Sports Networks (before Sports Channel New England joined Fox Sports Net), after that, until early 2006, NESN carried ESPNews in the afternoon and overnight hours.
Split into simpler sentences: NESN was, for a time, the New England carrier for Fox Sports Networks (before Sports Channel New England joined Fox Sports Net). After that, until early 2006, NESN carried ESPNews during the afternoon and overnight hours.