I haven't read either of these books (word is that The Da Vinci Code is nothing special), but something struck me as very wrong with the claim here. Perhaps New Zealand copyright law is dramatically different from ours, but in America you couldn't find infringement just because someone used your factual research as material for a fictional work (see Nash v. CBS, Inc., 899 F.2d 1537 (7th Cir. 1990)).
There might be a right of publicity claim for the use of the names and likenesses of the authors, but that's extremely tenuous. These snobbish profs should get over themselves and realize that the associate of their work with Brown's novel will doubtlessly increase their royalties, just as Brown's mention of various historical sites has increased tourism to previously unpopular areas.