First thought was "homeplug", but:
http://www.homeplugs.co.uk/acatalog/faqs.html
Going to outbuildings with them is not certain, as the consumer box and cable length may lose too much signal.
So maybe wireless using gain antennas is the best way - not sure if you can use a directional + non directional combination in "MiMo".
For the cable route, use a top grade surge protector with network protection at both ends, preferably one with a "connected equipment warranty"