The investigating officer must have been new because he should have charged you with S.130 Careless Driving. There is a reasonable prospect for a conviction for the Careless, but zero prospect to get convicted for 'Following Too Closely' based on what you've described.
You can do some research and fight this yourself; any decent paralegal willing to go to trial should get this withdrawn/dismissed. Also don't make a stink about this before the 6 month statue of limitation, because the prosecutor can change the charge to 'Careless Driving' within six months of the accident through a Part III Summons.
6mth Limitation:
http://www.e-laws.gov.on.ca/html/statutes/english/elaws_statutes_90p33_e.htm#BK103
Part III Summons:
http://www.e-laws.gov.on.ca/html/statutes/english/elaws_statutes_90p33_e.htm#BK36
Regina v. Ouseley, 1973 CanLII 663 (ON CA) [COURT OF APPEAL]
http://canlii.ca/t/g182x
The mere fact of a rear-end collision is insufficient to make out a prima facie case that the accused was following too closely contrary to s. 105(1) of the Highway Traffic Act, R.S.O. 1970, c. 202.
Gale, C.J.O.:-- The respondent was acquitted on appeal by trial de novo on a charge that he contravened s. 105(1) of the Highway Traffic Act, R.S.O. 1970, c. 202. In part, that section is in these terms:
105(1) The driver or operator of a motor vehicle shall not follow another vehicle more closely than is reasonable and prudent having due regard for the speed of such vehicle and the traffic on and the conditions of the highway.
At the trial it was proved that the respondent's car struck another vehicle which it was following, and that the driver of the lead vehicle had occasion to slow down gradually and stop just before the impact. There was no evidence whatever, apart from the impact, as to how closely behind the lead car the respondent's car was being driven at any time. As part of the Crown's case there was introduced a statement b y the respondent to the following effect: "I saw her brake ahead of me. I braked and started to skid and hit her." There was also evidence that the surface of the street was icy and not in good condition.
Mr. Campbell, on behalf of the Crown, asserts that i n those circumstances the Crown had made out a prima facie case. We do not agree. His proposition would go so far as to suggest that on each occasion where a rear-end collision occurs, at some fleeting second, the following car committed an offence under s. 105(1) of the Highway Traffic Act, and that nothing more need be proved than th e fact of the collision. In our view, the impact itself would sustain logical inferences other than that the respondent was following too closely and contravened s. 105(1). The trial Judge held, and we agree with him, that the collision may have been caused, quite logically, by inattention on the part of the respondent, or by excessive speed by him. He was not charged with careless driving, however, and we can see no reason why he should have been convicted of this offence, where there was no evidence whatever as to the distance which separated the two cars until the actual impact.