The threat of court sanction would be enough to ensure the new owner of a key east coast freight facility did not exploit its powerful position to the detriment of competitors, the judge behind a landmark case has said.

Federal Court judge Jonathan Beach on Thursday night released his detailed reasons for dismissing the competition watchdog's claims that rail company Pacific National would have a stranglehold on Queensland rail freight market if it bought a key transport terminal from fellow operator Aurizon.

ACCC chairman Rod Sims has argued strongly against the sale.CREDIT:NIC WALKER

Justice Beach had on Wednesday ruled against the Australian Competition and Consumer Commission's (ACCC) attempt to block the sale of Aurizon's Acacia Ridge internodal terminal near Brisbane.

The terminal is a vital part of Australia’s transport infrastructure as it is where rail freight can be transferred between NSW's standard rail gauge and Queensland's narrow gauge network, or moved off or onto trucks.

Justice Beach said he would have found in favour of the ACCC if not for undertakings Pacific National gave the court to guarantee fair access to the terminal by new competitors.

The ACCC argued against the effectiveness of these undertakings, saying Pacific National would still have the discretion to subtly frustrate and discriminate against competitors while not breaching the undertaking.

In his written reasons for the decision, Justice Beach said the ACCC had "considerably exaggerated" the extent to which Pacific National could use the terminal to disrupt any competitor trying to challenge it in the Queensland rail market.

"[Pacific National] has an incentive to operate the [terminal] in an efficient manner which maximises the throughput," Mr Beach said.