Electric transmission, telephone or telegraph lines, pole lines, railways, ditches, sewers, water, heat, or pipelines, gas mains, flumes, or other structures outside of the limits of any municipality which under the laws of this state, may be constructed, placed, or maintained across or along any highway which is a part of the state highway system, by any person, persons, corporation, limited liability company, or subdivision of the state, may be so maintained or constructed only in accordance with such regulations as may be prescribed by the department, which has power to prescribe and enforce reasonable rules and regulations with reference to the placing and maintaining along, across, or on any such state highway any of the utilities hereinbefore set forth. Nothing herein restricts the action of public authorities in extraordinary emergencies. Nothing in this chapter contained may be construed as modifying or abridging the powers conferred upon the public service commission in title 49, the intent of this section being that the powers hereby granted to the department may be exercised only in such manner as not to conflict with valid exercise by the public service commission of the powers granted to it.