No they can't, Stanleys isn't in the leasehold.IMO the most feasible solution would be some form of ropeway transportation, like a gondola or aerial tram from Bullocks Flat to Friday Flat. Trains are prohibitively expensive and building a track will damage the environment, and widening the road only makes winter accidents and carpark pressures worse.
However, as discussed in another thread (I think in the Thredbo development bang a gong thread), even ropeway transportation is very expensive. A 13km 10 gondola would have the capacity needed, but would take at least 36 minutes (if travelling at 6m/s) and could cost the best part of $100 million. For comparison, the Cablebus, a 9.2km Doppelmayr gondola in Mexico City, cost $108 million USD. Add in annual maintenance costs, and you've got a very expensive project for the government to build and operate.
Building this infrastructure, regardless of whether it's in train or cableway or road form, puts more pressure on the resorts. They can upgrade the lifts but at a certain point the runs become full. I don't go to Perisher enough to know what it's like there, but Thredbo could easily expand into Stanleys. Put in a lift heading up the ridge and a connector lift from Merritts or FF, and you're done. Of course, this once again is very expensive and and causes massive amounts of damage to a previously undisturbed area.
The SAP said it would support both a transport system, such as a gondola, into the resorts, and it said it would support resort expansion in the future if year-round use would be viable. Thredbo fits the bill on both counts. I personally doubt any of it will happen because of how expensive it all is, and because of how much money KT is about to spend on lifts anyway.
If they're going to put in transport, which they should, it should be a ropeway. It's far too expensive for it to happen IMO. The government may push Thredbo to expand in the coming years. I hope it doesn't happen because of the damage it will cause, but it might happen.