Real-time data for CBD and South East Light Rail routes L2/L3/LX is now available via GTFS/R feeds and Trip Planner APIs.
The GTFS/R endpoints are:
https://api.transport.nsw.gov.au/v1/gtfs/schedule/lightrail/cbdandsoutheast
https://api.transport.nsw.gov.au/v1/gtfs/realtime/lightrail/cbdandsoutheast
https://api.transport.nsw.gov.au/v1/gtfs/vehiclepos/lightrail/cbdandsoutheast
https://api.transport.nsw.gov.au/v1/gtfs/alerts/lightrail/cbdandsoutheast
If you are decoding additional vehicle information in the vehicle position feed, you will need to use extension 1999 proto definition available here