@JaceK a few questions, because whithout these answers, I can't understand the majority that you are saying:
First. what is a NDA?
second what is the SMS project that you're saying that you where working on it?
Next why the car makers have problems with audio cues on games if that cues aren't of them?
So, if the maker have problem with a audio resource... so, they have to give problems to you for add some visuals to the arround of the track like ground type, threes,rocks, and other assets. An audio cue will be simple and other more asset in the game.
Respecting the multiply sounds on a game... Well, isn't a very good example, but top speed have various of these sounds that are you saying at the same time, and we can play it without problems. Engine of your car (a fake engine but so well) a copilot, other car engines, and a weather. Add a more audio cue, like the RAD project does, instead of a copilot isn't a bad idea.
But well. Aparently you are turning arround various things of that problem, because a previous personal bad experience, but well.