I have no Canadian Hemlocks here in East Texas to work with, so I am not very knowlegeable about that specie in particular, but when you prepared your hole did you backfill with the existing soil, or did you fill it with soil from another location (bagged soil from the nursery for example). When you say it was a bareroot transplant, I assume there was no existing soil on the rootball when you transplanted. A transplant that has no preexisting soil on its rootball will be much more succeptable to stress than one with soil on its rootball. Transplanting is a major ordeal for a tree and causes a lot of stress.
If the tree had needles on it when you got it, it wasn't dead. How many trees did you plant all together and where did they come from. Are they from wild stock or are they from a nursery? A tree that was germinated from seed and has lived its entire life up to this point in a container will usually be less stressed throughout the transplant process than one that is transplanted from the wild.
These trees may not even be dead. If they were mine, I would monitor them about once a week (if they are still alive). It is not all that uncommon for a tree to loose its foliage during stressful times and refoliate the following season. Find a twig from recent growth and gently bend it. If it bends easily, your tree is still alive and may come back. If it snaps, it is dead. If the tree is still alive, consider composting and mulching.