Are electric knives used in foodservice?
I would consider the professional equivalent of the electric carving knife to be the meat slicer, i.e. the rotating blade device most often seen behind the deli counter.

At home, to break down a roast bird, take the meat off of a lamb-leg, etc., a good manual knife is most likely the proper tool.

If, on the other hand, I have a large ham (cooked or cold), or some other chunk of boneless meat that I want to slice more-or-less uniformly, then I will break out my electric knife.  For the home user, it is a fairly practical device, not taking up too much space, etc.

But its uniformity and speed cannot compare to the slicer.  As to a professional kitchen, you may or may not find one there.  Certainly in deli-type restaurants you would have them.  In a more traditional restaurant they are not as concerned with quick production of sliced meat, so any slicing is probably done by hand.