In my experience as a passenger, the obligation to stranded passengers is taken about as seriously as acceptance of valid tickets is. On parts of the railway the NRCoT is not considered to be worth the paper it's written on.
I don't know. If anyone gets stranded at my station, perhaps by someting like the last train of the day departing any earlier than T-30 or the rail replacement bus fails to materialise (definitely more a probability than a possibility) then I'm assisting them with the means the company provides with no hesitation whatsoever. Hey, I'll even call taxis for people if an airport train is cancelled at short notice and it'd be quicker for them than waiting for the next one.
But elsewhere on the network I've found some try and get rid of the problem of a stranded passenger by telling the customer to find their own taxi then make a claim to customer services or worse still, lying about non-existent connections from other stations.
I was down in the South East a few months back and regularly get the penultimate train back into London. On this occasion the last 2 trains of the day were cancelled, tree on the line or something. When I asked for help at the station I was told I'd have to source my own taxi. I then used the help point to get help from control, who usefully redirected me to the station staff.
Another time in the recent past, I was travelling from Brum to Ashford. I was on the 2115 from Snow Hill which should have gotten to Marylebone at around 2312. However Chiltern made the decision to hold the train at Banbury, join it up with a later service from Stratford and run it as a stopping service without a word of communication to the passengers. The yellow help point on the platform at Banbury didn't work and I had to find out from the relief driver what was going on. We arrived at Marylebone at 0006, no chance of getting to St Pancras for the last train at 0012. I tracked down a member of staff, a manager and explained I had been delayed. He refused to believe what had happened and said I must be mistaken. Eventually he checked on his phone and found a service from Victoria to Ashford. I asked him what time it was due to leave and he said "you've got half an hour, you'd better go" and ran off before I had a chance to say anything else. This was a lie - I later discovered that at that moment it was actually leaving in 18 minutes - and at that time of day, headways on the tube are 8-10 minutes. Far be it for a station manager to realise that not everyone can sprint like an olympian, dart through tunnels, run up escalators and make an accurate trajectory out of Victoria tube station to an unknown platform for an unknown service - whilst wielding luggage.
I've always held Chiltern in exceptionally high regard and was actually very surprised at how things panned out. If an driver unavailable at short notice means two services have to be merged into one, causing an hour's delay to one of the trains then come on, communicate that to the passengers and help anyone that is stranded by that decision.
I can only imagine that this kind of thing happens and goes unreported but it's just another part of the CoT that a passenger needs good fortune to have upheld and is something that really needs working on.