Weekly oil shipments by rail can be found on the web at Weekly Carload Reports. And a summation of that data with charts can be found at Association of American Railroads Freight Rail Traffic Data.
Crude oil by rail basically started with the shale boom. Prior to that almost all oil was shipped by pipeline. Of course a lot of oil was trucked to the pipelines. The EIA says in the first seven months of 2014 8 percent of all us crude and refined products was shipped by rail. It looks like that percentage was increased somewhat in the second half of 2014.