A spokesperson for Deutsche Bahn declined to comment.
Schenker, which provides logistics for sea, land and air freight, recently accounted for more than a third of Deutsche Bahn's sales.
"The cash flows generated as part of a sale remain entirely within the Deutsche Bahn Group," the proposal document continues.
Tough financing conditions could also lead to a decision not to sell, particularly if Deutsche Bahn is not satisfied with price, two sources said.
Private equity would struggle to finance such an amount unless Deutsche Bahn decided to part with a minority stake instead, this source added.