The proposed changes, introduced into Parliament last week by Treasurer Dominic Perrottet, would move rail assets such as tracks, trains, stations and land owned by RailCorp into a state-owned corporation with a commercial focus.

Rail operators such as Sydney Trains and NSW Trainlink would remain owned and run by the government.

But the opposition says the changes, contained in amendments to the Transport Administration Act, could help facilitate the future privatisation of rail services.

"We are saying that this bill makes it easier and essentially sets it up," said Labor's treasury spokesman Ryan Park.

The trigger for the overhaul, however, appears to be advice from the Australian Bureau of Statistics that current treatment of the state's rail assets and liabilities is insufficient for them to be listed off the budget books.

The changes in the bill, therefore, would be needed to preserve the government's budget position.

"Franchising is not the purpose of this bill," Transport Minister Andrew Constance said. He said the bill reflected the government's policy, announced in the 2015-16 budget, to establish a dedicated transport asset manager.

Labor has also questioned the safety impact of the changes. Under the current Transport Administration Act, maintaining "safe and reliable" rail services is listed as an objective of RailCorp - which owns rail assets - that is "more important" than other objectives.

But Mr Perrottet's bill says each of the objectives of the Transport Asset Holding Entity, the intended state-owned corporation, is to be of "equal importance".

Mr Park said the government was attempting to rush the bill through Parliament before the June budget.

Mr Perrottet told Parliament the bill would enable a more "commercial" approach to the management of transport assets.

"Being commercial in the management of public transport assets means being more transparent about the way the state funds and accounts for these activities," Mr Perrottet said.

"Nothing in this bill will change staff employment arrangements in Sydney Trains or NSW Trains. Nothing in this bill will change the framework for setting public transport fares, as this will remain to be determined by Transport for NSW," he said.

Privatising or "franchising" operation of parts of the state's rail system has long been discussed in the NSW bureaucracy, and in business.

The Berejiklian government is already privatising operation of the Epping- to-Chatswood rail line and the Bankstown line, which will be handed over to the company running trains on the Sydney Metro project.

Because of the complexity of Sydney's train system, the other section most likely to be targeted for privatisation is the Eastern Suburbs and Illawarra line. This segment of the rail system largely operates independently of the rest.