Theoretically any stress, illness, surgery, etc. can start an episode of shingles, so in that sense a hair transplant could conceivablly trigger an event. It would be an unlikely occurance however and the risk should be quite small.

Shingles is caused by the same virus that caused your "chicken pox" when you were a child. Following your chicken pox outbreak, this virus never leaves your body, but resides in a nerve root (for you this was the trigeminal nerve- the most common nerve affected). This virus can reactivate later in life to cause herpes zoster (shingles). However it is almost unheard of to have a recurrence of shingles. In matter of fact, there has never been a "proved" case of recurrent herpes zoster. The recurrent cases that have been cultured turned out to be herpes simplex, not herpes zoster.
Sincerely,
Paul J. McAndrews, M.D.
Diplomate, American Board of Dermatology