The problem with the ACCC is that they did not look closely enough that there is no opt-out. Freehills used one language, practice and implementation is different.
There is no (reasonable) excuse for redacting how the charge was calculated.
I have no idea, but wonder if fitting your own tag, and crunching a bit of lead foil or carefully crafted drink can/faraday cage around the toll tag might work.
Your right to ring them up and tell them your number plate for the day should also not be compromised.
Were I the ACCC I would ask the question: What other options are there?, without dumbly accepting the path put in front of their noses.