> So no one is camping out on the platform, for long.
I've never been in the Paris métro after it shut down, but are you saying the homeless people camping in some stations in the evenings, wrapped in their sleeping bags, get up at 1 a.m. and file out? I somehow doubt that.
I have spent a couple of nights in locked metro stations myself : before locking, they just warn that they're going to lock. Whoever's still inside is locked in until morning, but there's no kicking out.
That must be one of the bigger stations like Châtelet. There are endless hallways and tunnels to hide in. A simpler 1-train station will have 2-4 exits and they will certainly put you out.
It depends on the station and season.
In winter, station masters have a higher tolerance for camping - and it's worth mentioning that it comes down to the decision of station controller, not the RATP.
And last time I was there the controllers were scanning passes quite frequently.