I understand that when scouts are moving forward they can't end their turn on the same space as another's scout and thus move forward one space, but what I don't understand is when a scout moves backwards during the encampment phase and lands on another scouts space can it remain there?
It would move backward to the first empty space. This is mentioned in the "Scout's Movement" paragraph on Page 8:
A Scout movement can never end on the same space as an opponent’s Scout because on the Route, only one Scout is permitted per space (except in Saint Louis, which is the starting space, and the first space of river). If this happens, the Scout moves forward to the next available space (possibly moving backward during the Encampment phase). Players may pass through an occupied space, however.