The doombuggies can somewhat be "reprogrammed" like Bruce said. For the rehab of the WDW HM, the doombuggies now face the portraits on the right wall in the old Sinister 11 Hall and turn a little towards the bride now.
However, its not that hard apparently to do your own reprogramming. If you rock back and forth enough, you will break the linkage to the track and your entire buggy will turn freely. I don't suggest this though. When it gets to the Unload area, it automatically stops the ride and they have to take the mansion down for a few hours to fix it.