This happened over 15 years ago in the Merchant Navy. SeaLink employed fully qualified 'temps' to make up Crew numbers 'in the cabin' so to speak.
The 'Tech Crew' was not reduced, supported by agency staff as qualified as perm employees.
I believe the RMT Union fought this tooth and nail and lost.
Still on my first week in training, RMT were there to get my subs..............................................