Collateral - hidden ending???

Okay so I'm really straying from the reason I set this Blog up now but I promise there's a new print coming very soon (as soon as I get the chance to finish the bugger). Anyway, I was watching this Michael Mann flick for the 2nd time last night with my lady and I was struck by something slightly bizarre.

For the first 3/4 of the film the tone is fairly serious and shot in an almost believable manner, albeit with Mann's trademark fast-paced action thriller antics. Jamie Foxx's mild mannered cab driver is befriended/kidnapped by Cruise's sociopathic hitman and forces him to be his companion on the journey. A sub-plot evolves of Cruise attempting to convince Foxx that nothing really matters and he should psychologically let go and escape the control of others/life. Eventually Foxx accepts this philosophy and, knowing that he can never realistically stop a professional killer any other way, flips his cab (when neither are wearing belts) causing it to spin several times which would obviously kill them both. Point proven, what a good ending, except...

...after this scene Cruise then emerges and runs off to try to kill, coincidently, a girl Foxx met earlier and fell in love with. Foxx then persues Cruise, saves the girl and takes out the trained killer in a shoot out. I'd argue that the film even changes genre at this point, going from exaggerated thriller to laughable action adventure.

Maybe I'm talking out my arse but I'm guessing Mann made the film he wanted and ended it with a car crash and the death of his 2 leads. The implausibility of the final 1/4 seems so great that I think he was sending out a wink to the film bods to hit the off button post crash. Okay I'll piss off now.