I am sorry to learn about your tree. This advice Did you water it every month in the winter and up until your irrigation was turned on? If not, it is surely dead. Not only was this a dry winter, ALL trees, especially new ones, need watering every month when there has not been at least a foot of snow. New trees are transplanted with only 10% of their roots!
You can tell if the tree is alive by gently scraping a branch with your fingernail, just enough to remove a thin strip of just the outer layer. It should be green underneath (cambium) if it is alive. If one branch seems dead, try another few. If there is green, water it very deeply around 2 feet from the trunk and inside that circle and some outside. Slowly and for a prolonged time is the best way to water.Wait a few hours, then and dig down at 2' and see how deep your water got. Make sure the soil is damp as deep as the tree ball was (probably about 18"). If not, water some more until it is damp down that far. Water the tree weekly and deeply until you see leaves. Then once your irrigation is on, check once a month that the water is enough for the tree. You need to baby the tree for the first 3 years.
Best of luck and I really hope it is just delayed!