The £4.9 billion deal to sell Derby-based train maker Bombardier Transportation to the French Alstom group has gone through.
The deal has seen the Litchurch Lane works, which employs 2,000, among the assets transferred to the new owner.
It was initially approved by EU regulators last July, and officially went through on Friday, January 29.
Alstom said the enlarged group had a combined revenue of around €15.7 billion (around £13.9 billion), and employs 75,000 people worldwide in 70 countries.
Unite the Union, which represents many employees at the works, saying it is keen to find out more about the plans of the new owners.
In December hundreds of workers at the Litchurch Lane works were laid off.
Unite regional officer Larry McGlinchey said: “The sale of Bombardier’s transportation business to Alstom opens a new chapter for the workers at the Derby plant.
“Unite is keen to establish from the new management team what its future business plans are in the post-Brexit world and how they may impact on our members.
“Securing employment for the future, and maintaining terms and conditions are Unite’s priorities.
“We wish to work constructively with the company for a prosperous future at a challenging time for the manufacturing sector in the East Midlands.”
Bombardier Inc, which owned Bombardier Transportation, made the decision to sell its rail business in order to focus on the jet market and reduce its huge debts.
Henri Poupart-Lafarge, chairman and CEO of Alstom, said: “Today is a unique moment for Alstom and the mobility sector worldwide, with the creation of a new global leader centred on smart and sustainable mobility.
“More than ever, the world has to engage in a deep environmental and social transition to be able to address the great challenges of urbanisation, equal opportunity for economic development and climate change.
“Transportation, essential to the working and social life but with great environmental impact is at the heart of this transition.
“Our responsibility, together with the 75,000 people of Alstom today, is to transform our unique set of assets created by this transaction into the enabler of this necessary transformation.
“Our responsibility is to bring the innovation required for such extreme challenges and that all communities throughout the world, as they are travelling to meet loved ones or to work, can have access to the same quality of service and efficiency, while caring for our planet.”