Valve's Source engine (and GoldSrc, HL1), which itself is heavily based on the Quake 3 engine, uses delta compression and prediction as well. This is part of what made Counter-Strike such a popular game, and still is today. Especially in the competitive gaming world.
Valve licensed Quake code from id, and GoldSrc/Source are descended from that. There is no Quake2 or Quake3 code, the improvements over Quake are pure Valve.
http://developer.valvesoftware.com/wiki/Source_Multiplayer_N...