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I've been noticing boosting ranks because of outbounds for months, so I'm not surprised by your observations. And as Google works on URL basis, I expect this works on URL basis as well.
Still, I wonder how much outbound anchor text is important. On one of my sites, on subitem pages I have not linked text "Official site about this item:" and then linked "http://www.the_site.com/" because it was the way I found best for my users, but maybe it would rank well if I linked both.