The firm designs and manufactures manganese steel castings, track panels, turnouts and crossings at five sites in the UK.
The business generated revenue of £55m in 2010 and had gross assets of £43m.
Balfour said it remained committed to its core role as a rail infrastructure contractor.
The disposal notice said: “Over the last few years, the procurement model has evolved in the provision of core services to our major UK rail clients, eliminating the competitive advantage of owning manufacturing capability and leading to the sale of the business.”
Manfred Leger, CEO of Balfour Beatty Rail, said: “In Progress Rail, we have found an industry partner who will develop the UK switching and crossing business further and will integrate it into their worldwide manufacturing programme.
“I am looking forward to working with Progress Rail as a strong supply chain partner for our global rail infrastructure contracting activities.”