There may well be laws in place to protect whistleblowers, but the reality is individuals, irrespective of union protection, would still be sacked, and maybe even prosecuted.
Besides, back in the real world, who do they blow to? Their bosses? The government? The media? As if that isn't already happening. This is a government-sponsored dispute. No point in doing it to the union either as they already know, and it's part of the issues of the industrial action. No point in 'blowing' to the ABC as it's part of their ongoing challenge to the government.
They could of course just get out of their cabs and just do it. So it makes the train slightly late ..... and makes Southern's figures look bad .... so what ? Strange they are prepared to disrupt the service defending the 'safety' of their customers but won't do the same to defend the rights of their less abled customers.