Many of the MBA colleges allow you to take decision about the specialization after completion of first year (If its a 2 year course)
Beside that it all depends on your interest. In case you are interested in working in different field at worst the organization wont take into consideration your prior work-ex and give you same post as a fresher.
Also it would be much better if you interact with people who have actually worked in design dept and then went to do an MBA. IF you can find someone from alstom itself he can give you great advice
All the best!
P.S.: I am sure if you search you can find answer to most of your queries so no need to open a new thread for it. Posting in old thread would ensure better response for your queries as well.
i'm javed b.tech, mech07..nitb... join alstom...got into design... which stream in mba will be a relevant choice... my job involve analysis n calculations...