Ariz. Rev. Stat. § 40-325
When the commission finds that the public convenience and necessity will be served by having connections made between the tracks of any two or more railroad corporations so that cars may readily be transferred from one to the other, the commission may order two or more such corporations owning or operating tracks of the same gauge to make physical connections at any and all crossings, and at all points where a railroad shall begin to terminate or run near to any other railroad. After the necessary franchise or permit has been secured from the city, county, or town, the commission may likewise order such physical connection, within such city, county, or town, between two or more railroads which enter the limits thereof. The commission shall by order direct whether the expense thereof shall be borne jointly or otherwise.
A.R.S. § 40-325