It has been confirmed that the proposed rail line to Western Sydney Airport will be deliver and delivered by Sydney Metro. This comes alongside information provided to us that the government intends for all new rail lines in Sydney to be of a Metro Rapid Transit Standard.
The project is expected to form a North-South spine in the outer west, between Tallawong in the North and Macurthur in the South via St Marys, Western Sydney Airport and Narrellan. A heavy rail connect from the South West Rail Link at Leppington is also expected to be built.
Transport NSW Blog 