The Crown has to prove that he was the driver. Of course it also serves him well to have a sworn affidavit from the "friend" that was driving up his sleeve. Given the fact that there are already conflicting accounts as to him being the driver or the back seat passenger is a good start for him. He can also submit to a Polygraph and then try to meet with the Police and Prosecutor beforehand to resolve the matter. If they believe him then great, if they don't then a trial date will be coming. Once at the trial reveal the affidavit then apologize to the Judge for wasting the Courts time since you did try to resolve this matter out of court with the Prosecutor and Police. If he is telling the truth and found innocent then he can move to file a case for compensation.
He can also meet with the Prosecutor's Boss (the person in charge of that office, I forget their official title) after he meets with the Prosecutor. Their Boss can withdraw the case. They don't want the embarrassment and they do keep a win lose tally. They also do not want a Judge berating them in Public either.
That sounds good but I was under the impression that compensation depended on the charges being malicious. This whole thing sounds fishy enough to warrant charges even if they don't result in a conviction. I don't go for the embarassment / tally thing either.