I'm not sure this works--I've watched my wife play Jackpot with Blast Notes and the Blast Notes points are not added to the Jackpot (I don't think she even gets jackpot points for the base notes destroyed by the blast.)
You do get the 300% Jackpot bonus for the note you land on. You see the triple value added to the Jackpot score at the center of the screen. However, the collateral damage from a Blast note is not part of the Jackpot score, but it is counted towards the normal game score. Keep an eye on that counter (the regular one in the upper-right) next time... it is normally frozen while Jackpot is in effect, unless you destroy other notes with a Blast.
That being said, I was talking about Jackpot + Flame.