There is a way they could. In mind only thing that will slow down the frontier is government taking control of the revenue.
So my proposal is AI companies decide which labs have come close to frontier and decide to slow it. Government decide to stop progress in that and they divide the revenue from all labs(for say 10 years), without any matter of where it is coming from. Any lab which reaches close to frontier gets a chunk in the pie. This will encourage labs to come close to the frontier but not dangerously close.
So my proposal is AI companies decide which labs have come close to frontier and decide to slow it. Government decide to stop progress in that and they divide the revenue from all labs(for say 10 years), without any matter of where it is coming from. Any lab which reaches close to frontier gets a chunk in the pie. This will encourage labs to come close to the frontier but not dangerously close.