Nothing in this section or section 161.20, 219.40, or 219.071 changes existing law relating to the rights and liabilities of a city, town, or county in connection with the construction or maintenance of a railroad crossing, grade separation, or signal system, or impairs the terms or conditions of an existing arrangement or agreement, or renewals of it, between a railroad company and a municipality for the maintenance of a railroad crossing, grade separation, or signal system.