Easement questions are extremely nuanced. There are several questions to be asked:
Was there ever an easement registered on title to your neighbour's property? If so, that would likely create an enduring right, provided that it was properly registered and hasn't expired.
Is the property still in registry? Or Land Titles Conversion Qualified? Or Land Titles Absolute? The Province has been converting, bit by bit, to land titles. Under Land Registry, if you used a particular access route in a particular manner, under particular circumstances, and for a particular period of time - usually ten years - then you might have established a prescriptive right-of-way by operation of the Real Property Limitations Act.
If the property has been converted to LTCQ, then you can still rely on prescriptive rights, under certain circumstances, provided that they were fully established prior to conversion. (i.e. If you make the necessary use for 9 years and 6 months, then the property converts, then you will never establish a prescriptive easement. If you made the necessary use for 10 years and 1 day before conversion, then the prescriptive easement is established and may be relied upon under LTCQ.) If the property is in LTA, then *only* registered interests in land are enforceable - an unregistered prescriptive easement would be unenforceable at that point, and you would have no rights at all if your interest isn't registered.
I would strongly suggest talking to a lawyer about this. They can do the necessary searches to determine whether or not there's a registered interest, and come to an opinion as to whether or not you may have an enforceable unregistered interest. It'll cost some money, but when the alternative is building a new road...it might be worth a shot. And one of your options will be to purchase an easement from your neighbour - see what the price is; it might be worthwhile.
(Actually, paying for your neighbour's legal fees may get some mileage, too. Many people are really paranoid about other people making use of their land, because they're vaguely familiar with the concept of "adverse possession", so they always refuse to let anyone else use it at all. Ironically, saying that the use of the property was by consent is a full defence to any claim for prescriptive rights, including adverse possession. Also, adverse possession is no longer possible under land titles, either.)