When you return to work in Canada, if you are only in Canada temporarily, you MAY be a non-resident, if you are a non-resident now, as opposed to simply being outside Canada. At the very least you should have an FM-3 and a Mexican drivers license. As long as you are a non-resident, you can operate a Mexican-plated car in Canada, and you can drive it into Canada with no problems. We have done it often. However, as soon as you are a resident of Canada (which is determined by the government, not by you, based on several factors), it is illegal for you to keep the car in Canada, and, if the car was manufactured for sale in Mexico, in all likelihood, it will be impossible to import it into Canada. Also, the insurance that you obtain for liability coverage NOB will contain a provision that it becomes void should you become a resident of Canada or the USA.
At the border, as long as you have some documentation supporting your claim to be a non-resident you will be allowed into Canada without problems, but that only addresses the question of whether you will be required to pay taxes at the border. As mentioned above, in all likelihood the car would not be eligible for importation, so you would not be allowed to drive the car into Canada, if you told the officials that you wanted to import the car. There are notice requirements for such importation, and several steps to follow prior to arrival at the border, including ensuring that the car is eligible for importation.
With the insurance issues and other concerns, I would not recommend trying to slip something past anyone, since the repercussions could far outweigh any possible convenience or savings of money. It may be far-fetched, but you could be considered to have smuggled the car into Canada and be subject to criminal prosecution, fines and penalties, plus if you had a serious accident and your insurance was denied, you could face significant financial obligations. The safest route would be to ask the Canadian government and the insurance company, in advance, whether you qualify as a non-resident for these purposes.