Since it is in a trust, is it ok that just the wife signs the easement?
Without a copy of the trust agreement we can't answer your question.
Have someone in you FI that is familiar with trusts review the trust agreement or have your attorney review it, but you should not proceed until you have a valid opinion on who is required to sign any transaction on behalf of the trust.
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The opinions expressed are mine and they are not to be taken as legal advice.