As I observed in my comment above, this article on French Mapping of New York and New England goes a long way to explaining the situation in the years and decades before the Seven Years' War.
Before the Seven Years' War, Quebec had been a province in New France. Rather than a straightforward, agreed boundary, the border between the British colonies in North America and New France might charitably be described as "disputed".
King Louis XIV had made New France a royal province in 1663. As Britain and France had expanded their North American colonies, Britain had colonised much the Atlantic seaboard, while France had colonised a large swathe of the interior, stretching from Canada to Louisiana. The British colonies restricted French access to the coast, while the provinces of New France prevented British expansion into the interior of North America. The situation in 1750 is summarised on the map below:
(source: Wikimedia Commons)
The "border" between the British colonies and New France at this stage was marked by a series of forts. The disputed nature of the border is illustrated by the example of the British fort at Oswego, which had been established in 1727 on what the French considered to be their territory.
The forts along the border also feature heavily in maps of the period, as discussed in the article on French mapping cited above. However, most of the border areas were relatively sparsely populated by European settlers. The French in particular had found it difficult to attract settlers to their new colonies. It seems that the image of New France among the population "back home" was an:
"Arctic wasteland with wild animals and savage Indians"
As tensions grew between Britain and France in the run up to the Seven Years' War, more forts were constructed which, in a sense, consolidated the line of the border. Even so, there was never a formal acknowledgement of the precise line of the border.
After the 1763 Treaty of Paris, which marked the end of the Seven Years' War, Britain gained control of most of New France, and also gained Florida from Spain. This meant they now controlled all of North America east of the Mississippi, and the question of the formerly disputed border became moot.
In fact, the first British Surveyor General of Quebec, Samuel Holland, had actually proposed a survey of all the British territories in North America in 1762 - the year before the Treaty of Paris was signed. This survey was eventually to be approved in 1764, an it was as a result of this survey that the boundary between Quebec and New York was formally established along the 45th Parallel.