I wonder the same thing. The essence of a collusion scheme is a commitment between counterparties not to defect. Pure information is insufficient to create such a commitment.
There are other ways to distort markets besides collusion, and maybe Realpage does one of them?
Part of the complaint is that RealPage actively discourages defection
> While some landlords might achieve higher profits by setting lower prices than recommended by the algorithm, it appears RealPage takes extensive measures to prevent such behavior. As alleged in the DOJ complaint, RealPage pushes its software users to turn on the auto-accept setting so that price recommendations are automatically accepted. The complaint also alleges that the process of rejecting a price recommendation can be onerous. For instance, in order to reject a recommendation from AIRM software, users must provide a “business” reason for doing so, and they must do so separately for each floorplan in the building. When it is costly for software users to override algorithmic recommendations, supracompetitive prices—prices above what would occur under normal competition—can be sustained.
There are other ways to distort markets besides collusion, and maybe Realpage does one of them?