not a separate gare they wanted to have a specific arrival bridge to go to the office.
about the perfectly safe I guess your colleagues disagreed and I also disagreed for having spent 20 year in st denis projects. but I guess im a russian troll :
https://www.lemonde.fr/banlieues/article/2013/01/24/la-sncf-...
https://www.lefigaro.fr/societes/2013/01/16/20005-20130116AR...
https://www.nouvelobs.com/rue89/rue89-vie-de-bureau/20140502...