To be clear, it's common for IRS mileage reimbursement rates to apply for driving for other than commutes (e.g. to drive to the airport or a customer site)--but not for a daily commute.
I can't edit my original comment anymore, but I was wrong. It's not government mandated, just regulated in the sense that there's an income tax break for any travel compensation up to 21ct per km. Most unionized (CAO) employers follow this exactly, and even non-union employers like my own follow this as far as I know.
Fun thing is that it's the same amount regardless of the mode of travel, so if you take your bike to work it's an extra $4/hr tax free income ;)
