Here is my amended idea, Wikitravel added some sort of "gotcha" asset to their site, and Wikivoyage scraped their site and sucked it up, and when it appeared on Wikivoyage, Wikitravel sent the DMCA.
I could not find WikiVoyage's registered DMCA agent so it is entirely possible that Bing didn't know who to send notice of the takedown too.
Basically there seems to be a lot of bad blood between the two sites and as silly as it is, DMCA is an excellent "sniping" tool for taking cheap shots at someone you don't like.