Layout migration is an important step in design reuse. This paper presents a cell swapping based methodology to migrate hierarchical layouts from one technology to another. The migrated layouts retain both layout hierarchy and swapped cell sanctity. The proposed methodology swaps cell instances, marks these instances as fixed, builds broken connectivity due to cell swapping, and then uses a variant of hierarchical compaction for layout migration. Specifically, constraints for cells marked as fixed are formulated differently from standard hierarchical compaction. This ensures that such cells are unaltered in the migrated layout. In this work, a layout migration engine is developed that supports hierarchical compaction with cell swapping. Using the aforementioned methodology, industrial designs are migrated across technologies with the layout migration engine.