I backed a company van into my own car and was told that I have to use my personal insurance. Is this true?
They said that since it was my own car that it was 50/50: I pay for my car they for the van (which was undamaged).
Not being a claims adjuster, I can't say exactly how this situation should play out. However, their assessment seems fair since it was your fault and your vehicle was damaged. The liability portion of your company's commercial policy would likely pay out if the damage had been done to someone else.
If you think they are treating you unfairly, your own insurance company could work on your behalf. Furthermore, you could always contact a lawyer to assist you since it involves a place of work.