I speak as an employee of Alstom at the Preston site between 1997 and 2012. Around 2001 this site, along with other Alstom UK sites, was sold to property company St Mowden, and was leased back with a lease that expires in 2018. Since 2003, when the manufacture of traction equipment for new build trains ceased there, Preston site has had a lot of unused capacity. Only the parts and renovation businesses remain there, which are transferring to Widnes.
2018 as a crunch date has therefore been known of for a long time. Around 2010 St Mowden sought outline planning permission for the Preston site for housing development. Alstom reassured its employees at the time that they should not worry, the site would remain for Alstom businesses until 2018. Alstom did not want to retain Preston site beyond 2018 as the buildings, despite a major revamp in the mid 90s, are in a poor state of repair and would require a major investment to continue in their present usage. Plus, St Mowden probably would not have agreed to a new lease since, as a property developer, they are more keen to develop the site with housing and recoup their original investment with a handsome return.
Alstom Widnes site was always developed with the Preston site closure in mind, but the Widnes site is seen as an expansion as it already has train refurbishment/building facilities, plus there is space and outline planning for adding more workshop space within the site when required. The merger of the Alstom and Siemens rail business could mean more potential uses of the Widnes site....
Though I am sad to see the Alstom site at Preston closing, it really does not now meet the present or future needs of the business. Its location really precludes its use as a modern new build assembly plant for trains.