There was probably an agreement for service signed by you or your predecessor in order to get electric service. It's terms may have included permission to place a pole. I would move carefully- if you demand that the pole be removed, they may just do that and leave you without service.

You might have better luck with this as a next step:

http://www.puc.state.or.us/PUC/about_us.shtml

It won't cost you anything to find out if they can help you, and they might have some information which could be useful to you.