I do not work for a utility but I can comment with some knowledge on the points that you raise. The collective bargaining agreement between the utility company and their employees usually does not address safety concerns regarding contractors or vendors. The utility company will often claim that contractor safety is not a legitimate issue of bargaining between them and their own employees.
Often utility companies want to distance themselves from the safety practices of contractors in the hope that they can be excused as a codefendant if the contractor has an accident.
Most, if not all Outside Locals in the IBEW have language in their contracts with the contractors that require that work be performed under the safety standards of the Local Union or the Utility company, which ever is higher.