Notwithstanding the provisions of other sections of this subdivision and subject to the provisions of N.H. Rev. Stat. § 231:157 and N.H. Rev. Stat. § 231:158, the commissioner of transportation on class I and III highways, and state maintained portions of class II highways, and the governing bodies of cities and towns and the county commissioners for unorganized places on class IV, V, and VI highways and town maintained portions of class II highways may declare any tree, either alive or dead, situated within the limits of highways, roads, or streets to be a public nuisance by reason of danger to the traveling public, spread of tree disease, or the reliability of equipment installed at or upon utility facilities authorized under N.H. Rev. Stat. § 231:160 or N.H. Rev. Stat. § 231:160-a. After such declaration by such authority and notice to the abutting landowner on whose property such tree is located the said authority shall within a reasonable time remove the same without compensation or cost to the abutter. However, no such declaration and notice shall be required when the delay entailed by such declaration and notice would pose an imminent threat to safety or property, including electric transmission and distribution lines. Nothing in this subdivision shall be construed to relieve the public utility companies of their accepted responsibility of tree trimming and tree removal for the protection of their lines, or for the construction of new lines, or to alter the provisions of N.H. Rev. Stat. § 231:150-182 in any manner. The state and municipal authorities may require of the public utilities owning lines which pass through or near a tree or trees which are condemned for removal as a public nuisance to assist in their removal at their expense by either the temporary removal of their lines or by causing to be removed at their expense the top portion of said tree or trees from a point below their lines.