Passengers are supposed to be on their Seat/ berths allotted to them. At the time of TTE checking tickets if passengers are found missing, for no explainable reasons, TTE is at liberty to allot the unoccupied berths/ seats to anyone.
So TTE need not wait for the next station for passengers.
If you want to board the train from a station other than booked one.
Please...
more... go to PRS counter with :
1- Request letter
2-Copy of ticket
3-copy of ID proof you intend to show on journey to TTE...
Else you run the risk of loosing whole ticket...Do not leave it to Chance...