Marcus,i have a book titled "Railways of Sri Lanka", written by David Hyatt. Abeautiful book, covering many aspects of railways in S/L, but not big on "names", not that type of book.
to quote David Hyatt from within the book...."No centralised archive of documents exists within SLR. Old documants do exist in various departments but they are not classified in any way and one previous senior official spoke of the disposal of many of the old documents during the 1790's......"
he mentions these other publications : The Ceylon Railway - The Story of it's Inception and Progress , by G.F.Perera (not likely available) The Ceylon Railways : One Hundred Years 1864-1964, by CGR, only 100 copies printed! A History of the Sri Lanka Government Railway, edited by L.S.de Silva also The Ceylon Government Railway - A descriptive and illustrated guide by Henry W Cave
As to census, they do exist but are not available to teh public.