Meh. The very few times I've contacted a company about one of their employee's driving, I've gotten a pretty positive response. No idea what actions were really taken, but they seemed to take me seriously.
Whenever I've contacted the police -- also rarely -- I'm also batting 1.000. Just today, the very officer that we had a negative encounter with a couple of months ago gave us an escort and a wave on a narrow, congested road back into town.
People are very responsive if you write an polite, but direct, note to them.
Which reminds me: I have to write a thank you note to the police.