"This [torsorophy] example opened our eyes, and over the next few months we noticed that URLs from Google search results would later appear in Bing with increasing frequency for all kinds of queries: popular queries, rare or unusual queries and misspelled queries. Even search results that we would consider mistakes of our algorithms started showing up on Bing."
That's the key. Not the honeypot. The honeypot was just a test to see if they could catch them red handed.
Bottom line is that Google looked at the statistics and found that Bing results were improbably similar to Google results. Maybe they're lying about this, but I doubt it.
There's not enough information to figure out exactly to what extent Google impacts Bing results, but I would bet a lot of money that in the Bing code base there is Google specific code that behaves along the lines of "if on google, do x" rather than some generic code that just targets all sites.