Typical. Actually it's illegal, that's why it's a unwritten rule. But what are you going to do? I've had the same thing happen to me when I quit a contractor. And it sucked because it limited my ability to make a living. I even got it on tape of a contractor threatening their employees that if they went with me then the MSO wouldn't hire them for six months. But I had a choice to either fight it, or suck it up and go elsewhere. I went else where. God will deal with them.
This is CABL.com posting #152105. Tiny Link: cabl.co/mNJt