You get a thing called a 'Pension Free Voucher' from centrelink. Once you do, give the great southern railway a call and ask them how much it would give you off the trip to perth. It may only take you free from MEL to ADC... I mean adelaide (pardon my old v/line training there. Oh... and if you want to go from Shepparton to Fish Creek, you'd be going from SHT to FCK ;)

You get one a year from centrelink. Alternatively the pension is valid for concession nation wide. Swoite!