Claim: Ulrich Prinz lists 500 works using the Bach motif and Malcolm Boyd also released a similar list with about the 1500 works.
Evidence: In a comprehensive study published in the catalogue for the 1985 exhibition "300 Jahre Johann Sebastian Bach" ("300 years of Johann Sebastian Bach") in Stuttgart, Germany, Ulrich Prinz lists 409 works by 330 composers from the 17th to the 20th century using the BACH motif. 
A similar list is available in Malcolm Boyd's volume on Bach: it also contains some 400 works.