How's this for overthinking it:
Movie orchestral scores, like the Incredibles one, are implied to not exist inside that world. We know that there isn't loud music playing while the Incedibles are fighting evil. We don't think there's actually loud music playing in ancient Rome during Gladiator, or an epic score playing over hidden PA speakers in Jurassic Park, timed to get epic at just the right moments. The only exception is when it's showed that the characters are listening to that audio (like in Guardians of the Galaxy and Chris Pratt's Walkman"
So why in the heck is the Incedibles score playing on a coaster dedicated to the Incredibles? Is it ever established that that's Mr. Incredibles theme song for a TV show or something that exists in that world?
In order for a ride to be convincing, things have to subconsciously make sense. BTMRR and the rockwork look more convincing that the rockwork you find in Six Flags because it was done in such a way where it looks like the train had no choice but to follow the path it goes, not vice versa. They made it look like they hacked away at the rock to install the track, they didn't make it look like the rockwork melted up like lava and creeped around the supports. This is something most people don't notice, they just accept it. This is the audio equivalent of that.
They should have a line in the pre show that talks about how they hired someone to record an epic soundtrack for this new coaster to have it make sense. How else would a soundtrack that doesn't exist inside the Incredible's world be heard in a ride that's supposed to take place inside their world?
This is the kind of thing that Imagineers used to think about. Inside the Haunted Mansion, we can see the ghosts performing the song that you hear. Inside Pirates of the Caribbean, we can see them singing the song. In Guardian's of the Galaxy Mission Breakout, we hear the rabbit mention something about music and plug in.
