A class action by families and victims of a horror bus crash that killed 10 people is likely to be expanded after the NSW government flagged it is likely to sue the company involved.

Driver Brett Andrew Button, 60, was sentenced in September to a maximum of 32 years behind bars over the crash in the NSW Hunter region in June 2023 that killed 10 people.

Survivors and family members of those who died have launched a class action against Transport for NSW alleging design failings in the roundabout.

The case came before the NSW Supreme Court for the first time on Friday, when Justice Peter Garling asked whether the state agency would file a cross-claim against Linq Buslines, the registered owner of the vehicle that Button was driving.

“I suspect that is highly likely, your honour,” Transport for NSW’s lawyer Brian Moroney said.

Garling pointed out that for Transport for NSW to defend the case completely, it would have to prove Button’s driving was the sole cause of the accident.

“If the plaintiffs can establish five per cent negligence on your client’s part, it doesn’t matter to them about the other 95 per cent,” he told Moroney.

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Button was driving while impaired by an opioid painkiller, taking 350 milligrams of tramadol on the day of the crash despite doctors telling him the daily maximum dose was 200 milligrams.

Barrister David O’Dowd said the class action would remain focused on suing Transport for NSW and would not include Linq in its claims.

Court documents include allegations the interchange where the crash took place had numerous design flaws, such as being elliptical instead of round. It also featured guard rails instead of run-off areas and a gutter that was a “tripping risk” for larger vehicles. The speed limit through the roundabout was also allegedly too high.

Moroney said Transport for NSW was busy compiling all design documents behind the Greta interchange before it filed a defence. A defence and the potential cross-claim against Linq is expected to be filed by January 17.

The class action will return to court on February 7.

AAP