I have never heard or seen one being used as Topiary but I can't say that I am at all surprised as Spruce is often used as Bonsai material. There are pictures of a few awesome *Bonsai Spruce* specimens with claim of 250 & 1000 years old in a classic Bonsai of Japan.

I have a few failed attempts to grow and train. If I remember correctly it regularly flushes out vegetative growth. I am very short of ideas to talk with you about culturing it. I think thou, with a healthy root system new growth should begin in no time at all.