Transplanting Black Bamboo

15 years ago I bought some lovely black bamboo from a garden centre and planted it. It grew very well as bamboo tends to do but a few years ago I moved house. However I still have the possibility of getting a clump of this bamboo and I would like to plant it in my new garden.
QUESTION: What is the best way to dig it up and when is the best time to plant it ...... plus any other tips would be gratefully received.
I live in the north of Italy in the foothills of the Alkps so fairly soon the ground will be frozen and remain so until about beginning April.
Thanks in advance.
Cheers,
varallo