This is (to my knowledge) the most relevant case regarding facts and copyright. Rural made a local phone book, and Feist made an aggregate phone book which wholesale copied Rural's listings (and presumably others).
In this case Rural did seed their phone book with fake listings as you describe. Feist copied the fake listings along with the legitimate listings and still won the case.
Some related legal precedent, discussion, and doctrines. Note in particular the "Sweat of the Brow" doctrine, which holds that rights may be granted "through simple diligence during the creation of a work...Substantial creativity or "originality" is not required." Looks like this doctrine was rejected in Feist v Rural.
This is (to my knowledge) the most relevant case regarding facts and copyright. Rural made a local phone book, and Feist made an aggregate phone book which wholesale copied Rural's listings (and presumably others).
In this case Rural did seed their phone book with fake listings as you describe. Feist copied the fake listings along with the legitimate listings and still won the case.