Wow...talk about some serious mind game potential.
First, to ChromePirate, the answer, I believe, is no. In melee bombs detonated on impact so they could be replaced much faster. In brawl they're timed, so even with bomb canceling (just continuously down b) you can only have a max of two bombs out at time, just because its still physically impossible to get a third out in time. so yea. thrilling.
But onto the good stuff.
I practiced this for awhile, and like Darkness mentioned, you can do pretty much anything out of a bomb cancel lag free. Now I know these are only early impressions from someone with 1 post, but I'm having high hopes with this. This can be one hell of a defensive AT (yes, an actual AT). It's pretty easy to learn, but mastering bomb canceling will surely be a difficult art when used correctly. Here's a relatively vague and rather poorly written scenario: Your opponent approaches from the ground, say Sheik (because she is Satan). Samus mines and falls backward. Not only will Sheik hesitate approaching on the ground now, but you've got some serious options available. You can do b-cancel to dash attack, which comes out unexpectedly FAST. You can b-cancel to dash grab, which when timed with the bomb detonating is borderline arousing. You can dash into upsmash, into an aerial, etc. The point is that although b-canceling probably shouldn't become part of Samus' dominant strategy, this can be extremely useful in frustrating aggressive opponents (i.e. sheiktards) and even edgeguarding (sending a bomb over the ledge and b-canceling into who knows what).
So am I just aimlessly speculating, or do you think b-canceling will actually be useful for competitive play?