I heard this during the radio broadcast on WFAN during yesterday's game. If I heard this correctly, and if this information they reported turns out to be accurate - it sounds like Einhorn made himself quite a good deal.
The deal requires the Mets to be solvent in the next three years. If the Mets are not solvent, Einhorn has the right of first refusal to buy a controlling stake in the team. If they are solvent, the Wilpons will pay him back his $200MM and Einhorn retains his minority ownership stake.
If this is correct, to translate into oversimplified terms - Einhorn is floating the Wilpons a $200MM loan. Instead of charging interest on the loan, he's repaid by getting a stake in the team. One of the covenants of the deal is that the team is solvent. If they're not solvent - the "default" is that he has the first right to take over control.
It's a winning situation for Einhorn. If the Mets turn things around financially in three years, he gets his $200MM back and he's got a stake in a profitable enterprise. If the Wilpons don't get their act together, he gets to take over the team and run it the way he wants to.