Nothing in this article shall be construed as depriving the commission of jurisdiction over interurban railroad companies or limiting its powers in any way, but all of the laws of this state which apply to railroads in general, and to street and suburban railroads in particular, shall, as far as applicable or appropriate, apply to interurban railroads, unless interurban railroads are expressly excluded from the provisions of such laws by the terms thereof. The benefits of this article shall extend to all companies incorporated in this state prior to August 19, 1916, with the power to build or operate electric street and suburban railroads and which, as of August 19, 1916, were operating street and suburban railroads partly in an incorporated city and extending through the country to another incorporated city, including those railroads which run between an incorporated city in Georgia and an incorporated city in an adjoining state. Nothing in this article shall be construed to impair any valid, subsisting contract existing as of August 16, 1921, between any municipality and any railroad company or any street or interurban railroad company. Nothing in this article shall operate to repeal any municipal ordinance existing as of August 16, 1921. The commission shall not have the power and authority under this article to increase fares on the lines of such companies which fares have been fixed by contract between such companies and any municipality prior to August 16, 1921.