they are hardy .I live in canada they will survive temps of -20 farenheit . but i wouldn,t plant them if the ground is frozen , or is going to freeze again soon.

DO NOT keep them inside. That is sure and certain death. If the soil thaws (Wednesday 46 predicted!) go ahead and plant. Then mulch extremely well and cross your fingers.

If the soil does not thaw, put them in an unheated garage. Keep lightly watered whenever you can.

I have a dwarf Alberta spruce that I potted up for the winter -- used one of those huge looks-like-terracotta lightweight foam planters. I used a blend of conifer needle compost and potting soil made especially for outdoor container plantings. It's doing great right now.

Also, I did the same thing with a bird's nest spruce, which is also doing fine. That one will get planted in the ground next spring, but keeping it as a container planting over the winter seems to be working out.