To be fair, 10yr Treasury yields were just barely negative on the day ahead of the 30yr bond auction.  Afterward, however, they're officially moving into positive territory.  Here are the stats on the auction:

• 30yr Bond Auction
  • High Yield: 3.165 vs 3.169 forecast
  • Bid-to-cover: 2.31 vs 2.38 average
  • Indirect Bid: 66.4% vs 61.5% average

These stats are actually relatively strong by the time we consider the seasonal pattern in bid-to-cover (i.e. mid-december auctions tend to have lower bid-to-cover.  10yr yields are half a bp lower on the day at 2.906%.  Fannie 4.0 MBS are outperforming slightly, up 3/32nds (0.09) at 101-03 (101.09).