Hi, I was offered a position as junior manager a year ago by one of Altran's subsidiary and after discussing with them what my job would actually be like, I turned down the offer. Let me explain, the job is to recruit engineers for whom you have no missions (waste their time with interviews) to get information on what they are working on where they are (the recruiter, a senior manager himself, told me to only look out for experienced hires 2-5 years exp) so that you can then call up the company they work at to offer them Altran's help to finish their project.
Now, they pay well, as a manager you can make a lot of money however, I couldn't have worked for people that act like this. For me they are nothing more than a "body shopping" company with no ethics.
By the way I am french myself, and you can find on the web many articles of people having worked there and describe what I wrote above in much more detail.
Good luck anyway