I couldn't find a case concerning Monopoly in general but here is one by Hasbro on copyright infringement for Play-Doh that is good law (precedent), on which the facts seem similar enough to apply.
Status: Positive or Neutral Judicial Treatment Positive or Neutral Judicial Treatment
*474 Hasbro Inc, Hasbro SA and Hasbro UK Ltd v 123 Nahrmittel GmbH and Marketing & Promotional Services Ltd
High Court of Justice, Chancery Division (England and Wales)
11 February 2011
 EWHC 199 (Ch)
 E.T.M.R. 25
Floyd J. :
February 11, 2011
Confusion; Declarations of invalidity; Descriptive names; Honest practices; Infringement; Passing off; Revocation; Trade marks
H1 Community and national trade marks—PLAY-DOH (Classes 16, 25, 28—toys and modelling compositions)—Use by competitor of strap line “The edible play dough”—Action for trade mark infringement and passing off—Counterclaim for declaration of invalidity and revocation—Mark held validly registered—Counterclaims rejected—Infringement found—Whether defence of honest commercial use—Defence dismissed.
H2 The claimant companies, which made and sold among other products a children’s pre-mixed modelling composition, marketed that product under the trade mark PLAY-DOH for which the first claimant was the registered proprietor of one Community trade mark in Classes 16, 25 and 28 and two United Kingdom trade marks, dating back to 1970 and 1986 respectively, for goods in Class 16. The first defendant manufactured abroad, and sold in the United Kingdom, a powdered dough mix under the name YUMMY DOUGH. The YUMMY DOUGH product was promoted in the United Kingdom as “The edible play dough”, these words being printed in a single strap line across the bottom of the packet (illustrated in the judgment). In addition to the strap line, the words “PLAY DOUGH MIX” appeared in the top left-hand corner of the YUMMY DOUGH packet and the words “COLOURED EDIBLE PLAY DOUGH MIX” appeared in a smaller type size than that of the strap line on the side of the packet.
H3 Alleging that the defendants’ importation and sale of its YUMMY DOUGH in packaging that alluded to their own PLAY-DOH trade mark constituted an infringement of the rights in their mark, the claimants commenced infringement proceedings against the defendant. Following an application for interim injunctive relief a consent order was made in which each of the defendants gave temporary undertakings “not to undertake any material re-brand prior to judgment or further order in this action ”. The undertakings were very wide and, if they were to be made permanent at trial, their effect would be to freeze the defendants’ marketing of YUMMY DOUGH within very tight constraints in perpetuity. *475
H4 At trial, the claimants’ case rested on two separate bases: (i) infringement of each of their registered trade marks; (ii) passing off, this claim being based on the goodwill which the claimants maintained that they had acquired through use of the PLAY-DOH mark in the United Kingdom. The defendants counterclaimed for: (i) a declaration that the claimants’ registered trade marks had been invalidly registered because they lacked distinctiveness or were descriptive, and (ii) revocation of the claimants’ registered trade marks on the basis that the words “play dough” had become a common term in the trade for the products in question or on account of the claimants’ inactivity. The defendants also raised a defence to the action for trade mark infringement that their use of the signs complained of was an indication of the kind of goods they sold and that such use was in accordance with honest practices in industrial commercial matters under art.6 of the Trade Mark Directive .
H5 Held , by the High Court, that the claimants’ trade marks were valid and that they had been infringed.