Hi Emil,
If you want to transform field data between tow defined coordinate systems:
1) Open TBC
2) Drag and drop your field JXL
3) Go to Project Settings -> Coordinate System -> Change
4) Your data should get recalculated.
To test it, after 2) but before 3) Select two random points from the point cloud. Draft a linestring between them.
Proceed with 3) and 4).
Points should have changed. But not the linestring, linesting should no longer start and stop at the exact points from the cloud.