I have been brining the so-called "pre-brined" or "injected" or "salt solution added" turkeys for 20 years. The "common thinking" says that they will be too salty if you brine them. I have never found that to be the case. It's all about equilibrium. Ignore that stuff, and brine them all. If you find your turkey turns out too salty for some reason, then don't do it anymore, but it's worth the risk to find out, rather than settle for bland turkey your whole life because of opinion which is based on probability, but not necessarily experience.