I don't think a modern rerun of Defense Scheme No. 1 is really a viable warplan, in the event that it was needed. The whole concept rests on a number of strategic assumptions (as do all such plans) that are no longer really applicable in the modern world. In particular, it assumes that it will take a decent amount of time to mobilize the United States for a war against Canada, and that help from the United Kingdom et. al. would be on the way and ready to tip the balance.
Looking at things now, a very different scenario. American aircraft staging out of the CONUS could easily flatten the Canadians, and there are too many (and those are too dispersed) to be easily eliminated in a preemptive strike. This sums up a lot of the dilemma. Canada is too large to defend at all points, almost all the really vital parts are within easy reach of American forces, it doesn't have the firepower or numbers to go toe to to with the US, and nobody is willing or able to bail them out.
So, where does this leave our Canadian defense planner? Well, there is asymetric warfare. The best option is probably to recognize a stand-up fight as a foregone conclusion. Canada can make a brave showing, but it cannot win. But if we went to other methods, things change. Canada is huge, and holding it all would be no mean feat (although one wonders how much the Americans would need to actively control). A relatively undefended border and an english-speaking populace would make raids on American territory easy enough. By turning Canada into another Northern Ireland, perhaps the Americans could be expelled.