Chef is for configuration management, not for surveillance.
Like they said... they can install surveillance stuff on your machine, but that was likely just as possible prior to introducing Chef into the picture.
It's likely that they just want to get (more?) efficient in how they do their operations work.
Since the company owns the equipment, there's not even an implied right to privacy. They own it, ALL of it. Assume everything is monitored, and behave accordingly.
I do Chef development. We've been asked to include monitoring software for some groups in my client's company. Just assume that's always the case, when you're using someone else's equipment.