It's all very contrived feeling isn't it? They all have these big grievances in their past and just happen to be talking about them, like when Sam mentioned Ryan, just randomly or how Jason keeps constantly mentioning how Charlie was (in so many words), stalking him. I mean, I've never heard a guy talk about his ex so much and in such a nasty, negative way, just randomly like that, oh and she just happens to be in the other house listening to him say it.
My two pennies worth is, whilst there is a semblance of 'reality' to the show, it is very heavily fabricated and set up in many ways. I'm guessing they know about the other house, I'm guessing some of the fall out stories are being hammed up (or even invented completely) and I think this is basically scripted, event wise, but what they say and do mostly is off the cuff or improvised, to maintain some semblance of the reality aspect.