As a sidebar, I was on the city council here from '96 to '07. More than once, we had to deal with the issue of employees taking vehicles home. Many of them lived outside the city limits. Some of them a good 15-20 miles away.
What you as a technician see, doesn't always gee-haw with what the IRS or management sees. When you have a hundred people taking vehicles home every night, there are issues.
Most likely, the "truck charge" is to keep you from being taxed for your ride to and from work, which the IRS does consider (in most cases) to be "income".