I spoke to a guy in NSW who used to do this freelance when the police used to pay you the value of the crop that you called in. A nice little earner. Apparently POL does it now.
Most of the patches are out in the National Park and not monitored by the crims, so most of the time it would be pretty safe from ground fire. He was only shot at once, and that was from a big organised crime patch that was set up with claymores and AK47 armed guards.
Might get a bit problematic if a couple of heavies arrive at midnight and ask if you are the pilot of VH-XYZ.
A couple of days with a Bambi and a few hundred gallons of roundup would solve the problem for months, but I've heard that is not politically acceptable.