Yeah, I agree that Fox/Falco wouldn't be able to get jab -> DTilt'ed unless they did some massive DI upwards on the jab or something. Just as a note, any smart Falco wouldn't underestimate a good Ike like San; I don't think you can rely on the element of surprise to work for you all the time, especially if they've seen you do it before.
But wow, Falco boards don't very detailed frame data at all for side+B... it only says that the first hitbox comes out on frame 21, but they don't say when you can actually grab the edge. Do the hitboxes trail behind Falco so they come out after he starts moving? I think that's the case, otherwise it would be very difficult to hit him out of side+B without clanking the majority of the time. Anyway, Kirk's thread says jab 1 has IASA frames at 17. Assuming that the hitbox doesn't trail behind Falco, you'll have at least 4 frames + however many frames of hitstun there is on Ike's jab, so I guess it's possible to get the edgehog in that case.
But yeah, if they DI up you can just do a full jab combo and screw them over depending on their DI and %. If they try to DI the first jab away and side+B to the edge, I guess it depends on whether we can get an edgehog fast enough.