re: Has anybody ever sold easement rights to a power/utility company?

Well, it is true that in LA the public and semi-public co-ops have limited rights of Eminent Domain. So yes, if you were holding up a giant economic development due to your Right of Way negotiation they could expropriate the right and then you are subject to an independent government appraiser's opinion of the Right of Way's market value at this time.

NEVERRAINS had some good advice, be tough when you negotiate but I wouldnt let this drag on too long then you might end up in the situation I outlined above...

Let us know how it goes