Cities don't have any money but what they take from the citizens.
Employees make contracts with cities.
Citizens don't can't or won't pay any more.
Employees don't have contracts with the citizens.
The same power that government has which allows it to compel citizens to pay taxes can be used against employees too, allowing them to not pay if they can't.
As a tax payer when push comes to shove I think there are better uses for my money than paying unrealistic pensions.