Huge tracks and deep trenches fitted with massive (as in several story high) cogs. Once in place, whenever we need to move the fragment, we would just need to release the brakes on the cogs, move them to the appropriate place along the track and then fix them in place. This should take much less time than the usual massive earthworks needed to alter the course of the city fragment.
Feel free to rename this device
Once constructed, the home fragment can be broadly geomantically altered with much less effort. This will dramatically reduce the BP cost of future geomantic actions based on how much fine tuning the task requires.
Part of this project is a repeatable design that can be applied to future fragments for a much smaller BP cost (2-3BP)