On the TGV from Luxembourg to France, there were no barriers. And nobody ever asked me for my ID; in one of the legs, they didn't even check our tickets.

I don't doubt they keep those manifests, but I've found very little actual control.

Brussels does have troops going around, which is unsettling, but I never saw them inside the actual station, nor stopping people entering it, even after that poor devil immolated himself last year.