Railway is railway; passenger, freight, WCRC, driver, guard, ASLEF, RMT, TSSA, Network Rail, contractors, even managers - I'll say good morning/afternoon to any of them, and stop for a natter if they want - it's interesting to hear from other parts of the railway. No one with an ID card is ever refused access to my kettle or my spare chair if they want to sit somewhere quiet out of the way of 'the punters' while waiting for a train!
I don't hold with putting unnecessary self imposed divisions between the staff in an already over divided industry.
It's a sad state of affairs when you work at a station as I do which is run by one TOC, has another TOC based there with a traincrew depot, has a freight traincrew depot/sidings, and a Network Rail S&T/PWay maintenance depot (and up until recently, a signalbox) and no one knows anything about anyone outside of their little silo with very few exceptions.
I made it my business when I started to get to know the traincrew, some of the NR maintenance staff, the MOMs, a few of the freight drivers etc and I feel much happier in my work as a result as there's always a friendly face about.