Alstom had announced on Friday that it had reached an agreement with Knorr-Bremse for a purchase price of around 630 million euros.
Alstom shares were up 1.49% at 15.33 euros at 08:07 GMT, having climbed as much as 6.7% at the start of the session. Knorr-Bremse shares were up 4.04% at the same time.
"We have reduced our earnings per share estimates by 2%, but the transaction marks an important step in the implementation of the group's €2 billion deleveraging program, which is expected to be further detailed on May 8," commented Deutsche Bank in a note.
JP Morgan sees the sale as positive for the stock, and expects it to have a dilutive effect of around 20 basis points on margins.
(Reported by Clément Martinot, written by Nathan Vifflin, edited by Kate Entringer)