I am seeing large differences in the indexed pages of one of my sites in 4 different DC's. Is something in the works at the big G?

I've just had a site leap into page 1 for all my targetted phrasese from nowhere (It has been top for allinanchor for the phrasese for some time). It was new in December last year, so maybe there's something going on with the sandbox...

None of my other sites have changed

Yes. Google is surely doing something recently.