I too have heard of annoucements of duronto trains being made at technical halts.... like at Khandala of Pune Nizamuddin Duronto Express.
This train is sleeper one... hence, if seats r vacant then people might be allowed to board with general ticket and onboard, they take the full sleeper class amount like I observed in Paschim express ,a general ticket passenger paid tte onboard and got a receipt as allowance to travel in a sleeper coach. In NGP duronto too, I have seen people sitting/standing near the door.. you might think that they are wait list passenger ... tough not sure.. but they certainly looked like the ones travelling without ticket or with general ticket and as there is no...
more... general class coach in duronto, they board sleeper coaches.
I saw them at Kalyan, while the train was passing.. so, later on at Kasara or Igatpuri, TTE might have got them down.