I heard that some particularly hardy varieties can even grow in Saskatchewan, so, yeah, definitely. (I transplanted two from my Trois-Rivières bunch to my backyard in Lévis a couple years ago, and they died but it's likely because I kinda botched the job, not because the climate there is too rough for them.) They don't seem too picky in terms of soil, but they seem to grow much faster in good soil (I'm starting to have a large sample of them in various locations). At first sight, it's all about whether or not the lowest winter temps kill them, and also a minimum bar for summer sunlight I'd guess (easy enough to meet, but maybe not in the very cloudiest areas of Atlantic Canada).
Also, just to be clear, we're all in agreement here - the possibility of growing black walnut is most definitely not a factor that allows a hard distinction between Central NB and "Eastern Mixed Forest", and the search for such a factor is still going on
