I guess the one you saw at LTT is something that's not available at most stations.I guess you are talking about this specific equipment,can be categorized as some sort of an 'Industrial Brush' used to clean the rolling stock of Railways.It's sort of a 'high power equipment'.I guess if one takes or looks at pitlines in a broader definition then even a washing plant would fall under it as an added 'sub-category'.Pitlines are also used to look after the under belly of a coach.
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To add - I am not sure if...
more... most stations use such high powered equipment at their yards since i never gone into a pitline but if they use the conventional method of washing the coaches using the pipes from which water may not come out with high pressure and also don't have the advantage of automated brushes as seen in here,may be that could be one reason as to why L.T.T has such a dedicated facility just at the fringes of their yard.
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Image - Taken by me.