The plaintiff is Elissa Wall, whose testimony once helped convict Warren Jeffs. Her attorneys contended the agreement was not improper and the case should proceed.
"There was never ever, ever an idea that they were going to muzzle someone so they can't testify, or tamper with the truth," Wall's attorney, Mike Worel said in court.
Third District Court Judge Keith Kelly said he would issue a ruling at a later date.
Wall is seeking $30 million to $40 million from the trust and other defendants, including Warren Jeffs and the Fundamentalist Church of Jesus Christ of Latter-Day Saints.
But only the United Effort Plan is defending the lawsuit and is presumably the only defendant with any assets to pay a judgment.
Wall was raised in the polygamous FLDS. She was 14 when she was forced to marry her 21-year-old cousin Allen Steed. Jeffs helped arrange the union.
Wall later left the marriage. Jeffs was charged in state court in St. George with rape as an accomplice. Wall's testimony helped convict him, and Jeffs received a sentence of life in prison. The Utah Supreme Court later overturned the verdict.
Steed was later charged with sex crimes, but the criminal case was settled in 2011 when Steed entered a plea in abeyance to a reduced charge and served 30 days in jail.
What UEP attorneys say they didn't discover until recently was the existence of a deal that Wall and Steed signed in 2011. Steed agreed to not assist the UEP in defending the lawsuit Wall filed against it over her forced marriage and what she says was rape. In return, Wall agreed not to oppose the resolution of Steed's criminal case.
The state took control of the UEP in 2005 out of concerns about mismanagement. The trust controls much of the land and property in Colorado City, Ariz., and Hildale, Utah. The court-appointed fiduciary, Bruce Wisan, has expressed concern that a large judgment against the trust could force the sale of land and homes.
Outside of court Wednesday, Wisan said he remains open to a "reasonable" settlement with Wall.
"The trust is valued at $110-120 million, why should she get a third of that?"
The lawsuit is titled MJ v. Warren Jeffs. Wall is MJ, but was given the moniker because the lawsuit centers on what happened when she was a minor. Wall was not present in court on Wednesday.