Keep in mind that if you're looking at a 2-day chart of MBS Prices, they will look lower today vs yesterday. In fact, this is only because April coupons are on the right side of the chart while March coupons are on the left. April coupons were always priced that much lower than March. We simply switch our focus on roll day, making it look like prices dropped. They did not.
As for the events underpinning the strength, there's nothing too dramatic afoot. Treasury yields followed Asian equities markets early in the overnight session and European bond markets in the second half. 10yr yields hit the domestic session roughly 1bp lower and have fallen another bp so far.
MBS's first move of the day was sideways to perfectly unchanged levels. They've since added 4 ticks (.125) in both Fannie 3.5s and 4.0s.
The only significant calendar event for bond markets hits at 1pm with the 10yr Note auction.