This is incorrect. Rust is a reaction of iron and oxygen. Salt accelerates the process because it is ionized, but not necessary. You can flash rust pure iron in

This is incorrect. Rust is a reaction of iron and oxygen. Salt accelerates the process because it is ionized, but not necessary. You can flash rust pure iron in seconds with distilled water. Furthermore, ice alone is basically inert at the timescales that we experience. It would take eons for pure ice to react enough for visible rust to form. Even if it was cold enough for salt water to freeze, the difference would be negligible because salt and water separate from each other as the water crystallizes into ice. Also, we salt the roads here. Our freeze/thaw cycle is more frequent allowing for rust reactions to occur throughout the season, whereas a colder climate will only see reactions in the spring. There is no shortage of rust here.