I'm trying to determine whether the adsense preview tool is showing actual ads that are available to adsense publishers (meaning ones who are opted into the content network) or if they draw ads from their entire adwords pool for some reason.

I'm researching an industry and trying to determine who, of the major players, are buying ads in the content network. Currently, the preview tool suggests most are... but if the preview tool is simply showing all adwords ads that match then this could cause a major problem for me if I move forward with the wrong assumption.

Anyone know for certain? Thoughts?