If you need a flat answer, probably 0% because it's irrelevant, the Lilliput route taxi could have been a stolen taxi, it could have been a stolen red plate taxi, it shouldn't make a difference what the plates of the route taxi say. If they're not being regulated enough to provide SAFE transportation for visitors yet they're safe for locals, then something needs to be done.
Sorry but if the only safe transportation you're advocating is private taxis in negril, then tourism is going to suffer considerably.
I for one view isolated incidents as being isolated incidents, if it's as big of a problem as you're making it out to be then there needs to be considerable changes.