The following photos were taken under the southern end of the Gladesville Bridge (the bridge itself is almost completely free of graffiti - almost, but not quite). These photos demonstrate the current disjointed approach to graffiti removal.
On the far right in the red box is a green Australia Post cabinet. In the yellow rectangle in the middle is a speedboat on a trailer. The red box on the left is around an Energy Australia substation. The red arrow pointing up to the left is indicating a small amount of graffiti on the bridge itself.
Here is substation number 4082, showing several tags.
Above it is one of the bridge abutments, showing several tags as well as the grey paint which is a sign of graffiti having been painted over previously.
Directly across the road from the substation is an Australia Post cabinet, with numerous tags.
Parked next to all of this is a speed boat, which someone has "decorated" with a yellow stripe.
The point of all this is that the bridge is looked after by the RTA, the substation by Energy Australia and the cabinet by Australia Post, and none of their efforts are co-ordinated. This site will never be completely cleaned because if one company cleans their asset, by the time the other two companies clean theirs, the first asset will be vandalised again.