Adani's Queensland coal ambitions still face serious challenges, with a major rail company declining to service its Galilee Basin project and a big investor pressuring another one to do likewise.

Key points: The ABC understands major rail company GWA "decided not to participate" in the coal project

The ABC understands major rail company GWA "decided not to participate" in the coal project Adani then decided to build a smaller rail line in a bid to fast-track the project

Adani then decided to build a smaller rail line in a bid to fast-track the project One of Aurizon's top five shareholders is now also pressuring the company not to provide services to Adani

The ABC has learned Genesee & Wyoming Australia (GWA) declined to participate in the Carmichael coal project, after Adani approached it to supply coal haulage services from its planned mine.

"GWA has previously been approached to service the Adani Carmichael project and we have decided not to participate," the company confirmed in a statement to the ABC.

The snub, which came before Adani decided to build a smaller rail line in a bid to fast-track the stalled project, has narrowed the energy giant's options as it looks to bring its mine to life.

Aurizon — one of only two remaining rail operators with capacity to haul Adani's coal — has come under intense pressure not to cut deals with it because of environmental concerns, and doubts from some key investors that the venture is "a viable commercial proposition".

Aurizon has the capacity to haul coal from the Carmichael mine to port almost 400 kilometres away. ( Supplied )

An Adani spokeswoman said it had "not approached the American railway operator GWA to work on our current narrow gauge rail solution, so the matter of whether this company will work with us is not applicable".

"After a nine-year journey that involved multiple robust scientific studies and legal challenges, the Carmichael Project now has the necessary approvals in place and construction has been underway for a number of weeks already, delivering jobs and opportunities for regional Australia," she said.

"Our activities are being advanced in accordance with the Coordinator-General's project requirements and our construction schedule."

'Adani does not represent a viable commercial proposition'

The ABC understands Adani's plans for its first coal mine, a modest 34-hectare open cut pit up to 30 metres deep, were approved in March and the company provided a $15.8 million bond for site rehabilitation.

Adani has also settled long-standing litigation with engineering firm AECOM Australia, which claimed it was owed over $20 million for work on the original Carmichael rail plan.

But a major shareholder in Aurizon — which along with GWA and Pacific National has capacity to haul coal from the Carmichael mine to port almost 400 kilometres away — has been lobbying strongly against deals with the miner.

UniSuper, one of Aurizon's top five shareholders, has called on the rail freight company to provide no services to Adani beyond what it is legally obliged to.

In an email obtained by the ABC, UniSuper earlier this year said it had engaged in top level talks with Aurizon over the issue.

"We are very aware of and sympathetic to the widespread member and community concern regarding Adani's proposed Carmichael Mine and any commercial relationship that may come into existence between Adani and Aurizon," the email said.

"UniSuper's investment in Aurizon pre-dates any prospect of a link to Adani. As you are aware, the monopolistic nature of Aurizon's assets, Aurizon is legally bound to provide access to its network.

"However, together with significant environmental concerns, it is our opinion that Adani does not represent a viable commercial proposition.

"We confirm that our Chief Investment Officer has been engaged with Aurizon at the highest levels to convey the concerns of our membership base and seek confirmation that any engagement by Aurizon with Adani is restricted to meeting minimum legal requirements."

Adani multi-million dollar dispute resolved

Adani and AECOM confirmed they had settled their multimillion-dollar dispute but neither would disclose the terms.

"The issues raised by the parties in those proceedings have now been resolved and both CRN and AECOM have discontinued their proceeding against the other," the Adani spokeswoman said.

The miner was ordered to pay $12 million dollars to AECOM by the Queensland Building and Construction Commission last December but challenged the ruling in the Supreme Court.

The legal action was discontinued on 2 August.

It came after an ABC investigation of Adani's financial position last month prompted the company to publicly insist all contractors had been paid during its 11 years of operating in Australia.

Construction giant John Holland was among other business that have claimed to have been short-changed by Adani, but lost a long-running stoush over disputed payments for work on Abbott Point Coal Terminal.

Adani faces criminal prosecution

It comes as a criminal prosecution of Adani gets underway in the Brisbane Magistrates Court today, where it is accused of misleading the state's environment department.

The site of the proposed rail corridor for Adani's Carmichael coal mine. ( ABC News: Josh Robertson )

The department alleges Adani provided false or misleading documents about mine site land clearing, and it could face a fine of up to $2.8 million.

The company has said the prosecution over an "administrative paperwork error" would have no bearing on the mine's progress.

But Jo Bragg, the chief executive of the Environmental Defenders Office Queensland, said it involved a "very serious criminal offence".

"This wasn't an administrative error and it wasn't self-reported. Our client [the environmental group Coast and Country] caught Adani red-handed, at best misleading and at worst outright lying to the Government," she said.

Ms Bragg said a guilty finding would provide "grounds for the Queensland Government to launch an investigation into Adani's suitable operator status, and cancel or suspend their suitable operator registration".

The EDO and Environmental Justice Australia called for changes to Queensland's suitable operator rules to allow the department to disqualify miners on the basis of environmental convictions overseas.