Just to clear things up, overtaking is not the same as counterflowing. Overtaking is perfectly legal on most roads (just read the stripes) as long as the conditions are favorable for such maneuvers.

Counterflowing merely means driving on the wrong side of the road with utter disregard for oncoming traffic and with no viable means of returning to your lane should the need arise (e.g. 18 wheeler approaching).

Bikes can 'filter' in between traffic when traffic is at a standstill. Otherwise, they should not.