Generally one can use a transformer in either direction, from an electrical perspective. As Martin noted, however, the transformer should be checked for proper grounding and isolation from the windings with proper equipment and people who know how to use and understand the equipment. It's not difficult to test, but the results may have to be interpreted according to your local codes. An electrician with industrial experience "should" be able to help. Perhaps a general one, but I'm not sure of that. If I recall correctly, one would use a "megger" for the test which can measure electrical leakage between windings and case.
If it's not fit for use, it probably contains quite a bit of copper and iron for scrap value, simply due to it's weight.