The program has become so popular that it exceeded the provincial subsidy in 2018-2019 by $2.5 million and is on track to exceed it again, this time by $10 million, in the fall, Verster said in his letter to the TTC.
He said a new agreement to save the program is needed by October.
“Metrolinx intends to adopt the aforementioned discount to GO fares even if the City of Toronto and TTC decide not to match the transfer discount on the TTC fare,” he wrote.
TTC spokesman Stuart Green said Tuesday that nothing had been finalized but noted that Metrolinx had advised the agency of “potential changes to this popular program.”
“We have not yet responded as we need to understand the unanticipated cost pressures on our operating budget and report those to our board,” he said in a statement.
In a report to the agency's board ahead of a meeting Wednesday, TTC CEO Rick Leary said a detailed cost-benefit analysis will be conducted before a decision is made in September.
“If the TTC continues with the program, there could be unanticipated budget pressures for the remainder of 2019 and all of 2020 due to the loss of the provincial subsidy,” Leary wrote.
NDP transit critic Jessica Bell criticized the government for cutting the subsidy, saying it should be promoting fare integration across transit systems in the region.
“Forcing commuters to dig into their pockets for an extra $1.50 per round-trip is going to hurt the monthly bottom-line for already-squeezed working people,” she said in a statement.