as it should be
Just because something connects to the internet, or is electronic, as in data card readers or is used for management purposes does not give permission for the organization, company or person behind them to use the data for those individual other purposes.
If the/a government wants to use electronic fare system it does not have right to track citizens with it. only later if the individual 'is found to be acting criminally' should they then seek to identify a user.
The Australian Federal Gov has a MyGov portal/website that other State Governments could use to provide permission from users to use their data, Opal itself has a website that it could have used to permit monitoring.
In fact many users use a loop-hole to get free travel, if funds are insufficient they get a
"low funds warning"
and the card is not debited, they just never refill or replenish the card.
So as long as this situation exists pensioners and students could have had a normal card with insufficient funds on it and travelled unmonitored.
All the Government need to do is debit the card to zero, and fail any further usage until funds are replenished,
The Transport department of NSW government actually advertises over the intercom at rail stations trying to encourage people to register, this would enable them to harass a traveller when fund are low and overcome the problem, they use the claim that funds are guaranteed if they loose their card, but the people they want to attract don't have much on their opal cards anyway.