Routes change depending on crowd control situations at the time of day, and also the time from the parade warehouse to the park. Spectro begins on M.S. so it is over sooner, and the crowd can prepare for Wishes. Where as DDCTP starts in frontierland, providing smooth crowd control near the big rides, and slightly slower down M.S., not to meniton the castle as the backdrop of the M.S. Stretch. It all is calculated based on factors such as backstage prep, crowd control, time of day, and audio sync. It can easily be reversed, but would take some tech. work to reverse the sound ques, as well as lighting (in spectro's case)
If you asking if the route can be completely changed, the answer is no, due to length of sidewalks, crowd control post and rope placements (those holes don't exist in the entire park). There is also the point of on-stage access, as well as storage facilities, which are located outside the railroad, between Pirates and Splash Mt. It is connected via path to the M.S. parade exit/entrance gate.