Update November 2015:
VicRoads advice is that this practice is not legal
ie. You are not allowed to lane filter between traffic and an adjacent kerb.

Update January 2016:
Further details here: Victoria – Motorcycle Filtering

Saw this recently

Legal but stupid

From the Victorian Safety Road Rules 2009

141 No overtaking etc. to the left of a vehicle
(1) A driver (except the rider of a bicycle) must not
overtake a vehicle to the left of the vehicle
(a) the driver is driving on a multi-lane road and
the vehicle can be safely overtaken in a
marked lane to the left of the vehicle; or
(b) the vehicle is turning right, or making a
U-turn from the centre of the road, and is
giving a right change of direction signal; or
(c) the vehicle is stationary and it is safe to
overtake to the left of the vehicle.

I did some hairy things when I worked as a motorcycle courier, but I would never have been as stupid as that.