Chennai EMU - என்னோட உயிர் டா நீ

The shared link is very interesting RTI case : click here
TTE and competant officer can allow passengers other than CNF/RAC ticket holders in some cases:click here
647. Staff authorized to grant permission to a passenger to occupy a seat/ berth.�No person other than that for whom accommodation has been reserved under the rules should occupy such accommodation except with the permission of an authorized railway servant The under noted staff are authorized to grant permission to a passenger to occupy a berth/seat previously reserved for another passenger�
(i)...
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At train originating stations or at stations where through carriages are attached or at stations which have a quota for reservation of berths/ seats. The official in charge of reservation present on the platform or in his absence, the Station Master on duty; and
(ii) At other stations .. .. The Conductor if there is one on the train or, in his absence, the Guard of the train.