Also note that working unauthorized overtime is usually a firing offense, even within the Federal Gubermint. Thus when the clock ticks over, drop what you are doing and go home. Even if it takes you an hour the next day to get back to the point you were at. And forget signing in from home to check email or the status of a computer run. Productivity costs will be enormous.
Look, too, to the conversion of knowledge workers to independent contractors. Companies get themselves out of the specter of overtime pay and shed the cost of benefits. Employees find themselves paying both sides of Social Security, replacing their health insurance and other benefits, and filing a business return. The workload remains the same but their income goes down dramatically.