There isn't a single reason that legitimates this sort of action, even to "protect your project from former employees". You can do that easily by having a backup server of anything that's being worked on, which is the Ubi way.
And yeah, to the best of my knowledge, Austrian laws (as with most EU countries) require some form of notice before being fired (unless you screwed up real bad).
What's this alleged title being mentioned? I thought they only worked on xbox ports...