I witnessed a police officer on mototcycle do this one day (zigzagging on the highway to keep all 6 lanes compliant). He rode like this for a few miles and then sped off (breaking the law, ass he did to also take the lead of the pack). I witnessed his full ride and never saw any traffic condition to warrant his morning commute behavior.
And I never saw him ticket any offenders who attempted (unsuccessfully) to pass him by going faster than 60MPH.
He never turned his flashing lights or siren on.
I live in West by God Virginia so we don't have too many problems but I have heard of the practice you describe used regularly by cops in Southern California in an attempt to create buffer zones in order to prevent gridlock. I have no idea if it works but there you go.
I was stuck in a pack of people on I-75 behind a couple of FHP cars doing this. It just shows how absurd the !@#$@!%$@ speed limits are in the first place. The sad thing is that nobody seems to care. I hope this film is enough to jog the heads of some folks in the U.S. I doubt it.