Thoughts from an HEMS pilot
Wires in an LZ present a significant hazard to HEMS operations. It's an especially difficult risk to manage when the right of way and support towers/poles are not in the pilot field of view View of right of way and towers are the most reliable method of locating the conductors and static lines. I have found that parking vehicles under wires present a useful reference and reminder of the obstacle's presence. This information is part of the LZ brief we train agencies to provide.
The usual method of vertical descents and ascents minimizes exposure to wire hazard seen and unseen, but present a serious challenge when the vertical segment is extended, as it would be in a valley or when there are multiple levels of hazard to navigate. Sometimes it is possible to avoid wires by direct visual observation without other references. I find this extremely difficult with smaller gauge wires, as they present little surface and texture for depth perception, and the stereoscopic physiologic function is least effective when most needed, as one passes the wire altitude.
An extensive vertical is also especially challenging with limited surface features available, as I would expect in the snowy terrain of this accident.