Many German rail staff, including almost all in public facing jobs, speak good, often excellent, English. I expect that the standard is a bit more varied for other jobs, but most would have a reasonable working knowledge. It is mainly in the old East Germany that you may still find older staff without much English. I would think that a reasonable standard of both spoken and written German, and an ability to read and understand the somewhat convoluted German grammar, would be an absolute necessity to get a job. In every job I have had abroad (none of them in Germany) a basic competence in the language was an absolutely necessary.