It would have to be a completely commercial operation, with a 99%-assured arrival time of 7.30am.
$500 fare (business class airfares $650 - $1000)
120-pass trains (individual berths with a few twins) = 120 x $500 = $60,000
2 trains per night (one each way) = 2 x $60,000 = $120,000
6 days per week (not Sat) = 6 x $120,000 = $720,000
50 weeks per year (not Christmas/New Year or Easter) = 50 x $720,000 = $36M
80% occupancy = $36M x 80% = $28.8M
less the (up to and not offset) $2.6M GST collected for the Government, leaves about $26M per annum to run the service, eg staff, capital costs, Wi-Fi, etc. There would be additional revenue (minus costs) from the lounge and dining cars.
It is very doubtful any private operator would take the risk.
Operating on board staff will need to be paid, but support staff could be partly volunteer.
I would also dispute there are so called people in heritage groups who know to look after business travellers. Its not shoe shine 1950's, you will need to hire and train people to meet todays standards of safety, corporate culture that you are trying to project and still provide a reasonable level of service to make people feel welcome. I suspect the dining cars would be buffet to save on waiting staff. The chef would simply be reheating food and placing in the buffet. Washing dishes, cleaning, making beds etc would be done by contractors at the end of the journey during the day.
But for a 7:30am arrival time, the train would leave at 9 - 9:30pm, so no dinner and likely no breakfast would need to be provided which would save alot of cost. Best to simply provide snacks with evening drinks and morning coffee etc.
120 pass of sleepers is about 5 pax cars, plus 2 other cars and a loco, total 8-9 vehicles @1L/vehicle/km = 7700L of diesel or nearly $10,000 per trip.
Wages, Assume 5 on board crew per train + 2 drivers (if using locos) + contractors to clean and service the train and food Looking at min $5000 per train trip.
Track fees? Assume 5c/t/km = $20,000
Train maintenance and depreciation costs = ?????
Insurance = ????
So known costs around $35,000 plus maintenance, insurance, redundancy (ie call bus when line blocked), I'd say easily exceed $50,000 per trip.
You can no longer rely on high levels of alcohol consumption for revenue as this is a business audience target and in this day and age even Corporate Australia doesn't tolerant people coming to work suffering hang-overs or alcohol breath.
There are few BC travellers on the flights between Syd and Mel and I'd dare so too many of there are interested in rail, the target audience is EC.
Rolling stock will be a major issue, only stock up to the task on NG is owned by GSR and the NSW govt (ie XPT). The retired XPT's could be rebuilt to 2 x BC only sleeper trains of 8 cars plus two locos per trains. Note four locos are only 30 years old.