[John Jarrold]

The major publishers certainly don't want a marketing plan from new authors. They have marketing departments who discuss what is to be done with the editor (and some of whom will be irritated if the author submits a plan, since it is their speciality). Editors will often discuss any marketing with the author in the lead-up to publication, should there be money in the annual marketing fund for their book.

As others have said, a publisher might ask you for contacts (other writers in the genre, friends in the book trade) for publicity purposes, but this is different from marketing. Basically: publicity is free, marketing costs money - although online marketing via your own website, etc., has changed this old saw somewhat.