It is actually common in big companies. The car allowance line allows them to separate from what is the normal salary in the contract. In some companies, employees have the choice of either the company car scheme (they get a company car with a leashold and they pay only part of the leashold as the company is paying the rest directly), or the car allowance (then they can buy whatever car they want and they get the money that the company will invest in the leashold anyway if you chose the first option).

Both are benefits that are added to your salary and taxed the same way for you.