I own a house in NY where the power company has an easement to run through there. (assume they have an easement). before I purchased the home an addition was put onto the back on the house. There is a 10' portion of the house that the powerlines run directly over. this concerns me. Id assume the lines were there before the addition. However, am not 100% sure. What are my rights here? Id talked to National Grid about moving them and they state "what was there first" told them I don't know and they want ~ $15k to move them.

what are my rights here?