MSN contracted with Yahoo for INK results and OVER sponsored ads. I believe but do not have proof that Yahoo will NOT share SLURP results, only INK results that they were contracted for.
Yahoo will simply be delivering results to MSN that they will not even put up front themselves.
Semel got one over on Gates with this move.
Notice how MSN revealed this week that they are staying committed to L$. Since January 15 LookSmart has been in front of INK in most results pages of MSN search.
I keep mentioning how my L$ campaigns are second only to Mamma.com in conversion rate.