Neither, actually. It is a provincial charge, under the Compulsory Automobile Insurance Act of Ontario (CAIA). Here's a link to the full text of the law:
http://www.e-laws.gov.on.ca/html/statut ... 0c25_e.htm
So same level as Highway Traffic Act, but not a criminal charge. The minimum fine is $5000, max fine $25 000 for the first offence. Sounds pretty steep, but before you get too worried about paying $5000, you should know that a Justice of the Peace can reduce the fine below the minimum in extenuating circumstances. Given the fact that you had recently separated, your ex didn't fulfill his obligations, etc., there's a good chance that $5000 would be the maximum that you'd pay. Depending on where the collision occurred, the JP might be fairly sympathetic and lower the fine. If you can show that, upon discovering that your ex wasn't paying for your insurance like he was supposed to, you immediately arranged for insurance, that will help, too. Getting the help of a paralegal might be a good idea, too. Did your insurance company ever provide you with any notice that your coverage was being terminated? Also, were you charged with any other offence as a result of the collision?