Complex sentence: The damaged units were initially towed back to the EMU depot north of Wellington station, where later the two undamaged halves-EM 1010 and ET 3223 (renumbered to ET 3010) were marshalled together as a unit.
Split into simpler sentences: The damaged units were towed back to the EMU depot north of Wellington station. Since then EM 1010 and ET 3223 (renumbered ET 3010) have been marshalled as a unit.