RTI? For what? What if he had two different tickets? Incase of separate tickets SM or any railway authority is not liable to allow him travel further on that ticket. Maybe on humanitarian grounds he may permit but certainly not liable. And even incase of BPT too, he will get seat in next train only if avbl. If seat is not avbl, he has to allow passenger to board next train and the pax can talk to TTE for seat/s