I would avoid old power poles for any use for fear of persistant toxic compounds. Creasote is a coal tar derivative that is classed as toxic, carcinogenic and mutagenic, a very nasty witches brew of a wide variety of organic compounds. Not only organics are of concern, I have an old materials of construction manual that describes the use of mercury additives as an industrial fungicide.
Beware, the cheap man sometimes pays the highest price.
