And though the accord quashes the litigation, it might not end questions over the April 2012 blaze at the estate, Bloomfield, which was built around 1885 and later redesigned by the renowned Philadelphia architect.
Radnor Township Fire Marshal Don Wood said Tuesday he stood by his original finding that the fire was of undetermined but not suspicious origin, although he could not be sure how it started.
"No one has given me anything that would cause me to change my ruling," Wood said in an interview.
The settlement proposal, pending approval of a Philadelphia federal judge, comes days after Batoff dumped his original lawyers in the case, and after those same lawyers filed sworn statements from experts who said the blaze was neither an accident nor an act of nature.
Batoff and his new counsel declined to comment.
In a statement released Wednesday by their lawyers, Topolinski and Charbonneau stressed that no independent investigation had upheld Batoff's claims of arson, allegations their lawyers called "wildly overblown" and vicious attempts to smear them. The couple's statement said they were pleased with the deal.
"From Day One, we have maintained - and the truth is - that the fire was a horrible accident," their statement said. "We are looking forward to rebuilding the house, using materials that were salvaged in the fire, and making it our family's home."
If the fire was a historic event for the ordinarily sedate township - more than 100 firefighters battled it - the aftermath was even less predictable.
In December, Batoff, son of former Democratic fund-raiser William Batoff, claimed to have the answer.
He asserted in a federal racketeering lawsuit that he had been the victim of an elaborate insurance-fraud plot hatched by Topolinski, a prominent businessman with varied interests including a printing plant in Swedesboro, and Charbonneau, an interior designer from Montreal.
The suit claimed the couple had agreed in 2011 to buy the property for $5.2 million only after Topolinski learned the property had an insurance value of $22 million.
Batoff paid $2.7 million for the property, records show. He was selling because he was divorcing, his lawyers have said.
Topolinski and Charbonneau moved in and began making lease payments, but dragged their feet on the sale, Batoff claimed, because their goal was something grander: at least $20 million in insurance money and control of a Main Line parcel prime for development.
The suit alleged the pair had dismissed the groundskeepers, disabled the security and surveillance system, and were responsible for a fire that started in a basement corner near the circuit panel that was certain to destroy the place but that would look like a wiring malfunction.
The suit accused Topolinski of orchestrating a similar insurance fraud in connection with vandalism at the South Jersey printing plant. No such charges have been filed.
And it said Topolinski and Charbonneau waited until the dust had settled - and the fire marshal made his ruling - before asserting that their sales agreement made them the rightful property owners and thus deserving of any insurance payout.
They won a significant victory on that front when U.S. District Judge William H. Yohn Jr. issued a temporary restraining order in October freezing $17.4 million left from the insurance money Batoff had already collected.
Yohn had been overseeing the litigation and the case seemed headed for trial. Last month, Topolinski's lawyers turned over more than 17,000 records and documents to Batoff's counsel, records show.
But things abruptly changed last week. On April 11, Batoff's lead lawyer, Paul Rosen, filed affidavits from two fire experts who examined the scene.
One, former Philadelphia Assistant Fire Marshal Louis Gahagan, traced the fire to two wires in the basement near the circuit breaker, according to his report, which was publicly accessible until Wednesday, when the judge ordered it sealed.
The second expert, New York engineer Shukri Souri, concluded the damage to those wires came from "an intentional external nonelectrical force," his report said.
The same day, Rosen and his partners on the case withdrew as lawyers for Batoff.
Reached by phone on Tuesday, Rosen declined to elaborate except to say: "The client is the person charged with making the business decisions on when and if he wants to accept a settlement, and that is his sole prerogative."
Contact John P. Martin at 215-925-2649, firstname.lastname@example.org, or follow @JPMartinInky on Twitter.