As a general rule with ESB, do not sign over absolute rights to them i.e. permanent rights to wayleave or, in the case of substations, giving them the parcel of land.
In the first instance, ESB usually sends out complete paperwork seeking permanent aquisition. You should get you solicitor to mark up this paperwork as a license/lease type arrangement rather than a permanent one. You have to bear in mind that the ESB may move their installations at some future date or technology/alternative routes may make them redundant. It may be decades in the future, but you're better off not having this problem. ESB legal department will usually accept license/lease agreements if the owner insists.