Fish and Game and the Historic Places Trust requested access to the land to carry out survey work "to gather a greater understanding of the galaxiids", the native fish in the tributaries.
The Fish and Game councils sought an amendment of the water conservation order on the Nevis to prevent damming or diversion of the river.
A special tribunal, appointed by the Ministry for the Environment, that heard the application recommended last August the order be changed to rule out damming or diversion.
The tribunal's finding was challenged by three submitters - Pioneer Generation, the Fish and Game councils and Whitewater New Zealand, a recreational kayaking group.
Counsel for New Zealand and Otago Fish and Game councils, Jackie St John, said the survey information was "critical".
The tribunal made the decision because of the presence of the Gollum galaxiid, found only in the Nevis River.
She said that if access could not be provided, it was important that any research carried out by Pioneer had a "methodology [that] won't be contested in the environment court".
Counsel for Pioneer Generation Kerry Smith said Pioneer had not received details of what Fish and Game was proposing.
"When, why, where, how long, what [are] they testing and what are they surveying? They asked to access private property with none of the background," he said.
In response to questions from Judge Jon Jackson, Mr Smith said he would have to take advice from Pioneer on whether it would allow access if Fish and Game provided details.
Judge Jackson said it would take a long time to get to a hearing if Pioneer was "going to play these sort of games".
"You can't have it both ways. Either you let Fish and Game go and do the work, or you go first."
He adjourned the case to the Environment Court in Christchurch next Wednesday, to allow the parties to discuss their options.
He could not order Pioneer to give access but there were other options, he said.
"... if Miss St John can't get anywhere in discussions with you, then I will apply for a briefing notice and deal with it very swiftly indeed."
Judge Jackson also adjourned late applications to file submissions from the Historic Places Trust and Alexandra residents John Douglas and Brian Patrick.
