I found an article in Resolution magazine (UK, they were handing out free copies at the AES 
Convention) that seems to explain the EMI split. Some highlights:

UMG got The Beatles, The Beach Boys, Abbey Road, the Capitol Tower, Katy Perry, apparently most of 
the Capitol back catalog, and more.

Warner Music got Pink Floyd, Jethro Tull, Cold Play, EMI Classics (including Angel and Capitol 
classical recordings) and apparently back-catalog material assoicated with Parlophone (I'm assuming 
that goes back to the Louis Armstrong sides and all the side that John Hammond produced for 
Parlophone in the 30's).

Warner paid a premium because some hedge funders and BMG got into the bidding late, some UMG's deal 
now looks better.

I noticed on HDTracks that titles formerly listing EMI Classics as the label now list Warner Erato. 
And there is now a Warner Classics website:

Industry observers seem happy that Warner ended up bigger, so they are a bit more of a counterweight 
to Sony and UMG.

-- Tom Fine