As you may know, Microsoft and Nokia signed a deal last month, aimed at creating a “third horse” in the smartphone race (alongside Apple’s iOS and Google’s Android platforms [kind of insulting to RIM, no?]). As part of the deal, the two companies indicated that Nokia Maps would become a core part of Microsoft’s mapping services, and would be integrated with Bing.

“Maps would be integrated with Microsoft’s Bing search engine and adCenter advertising platform to form a unique local search and advertising experience,” the press release said.

That integration might be much bigger than anyone realized, however.

Greg Sterling at Search Engine Land says he had lunch with a “person with close connections to Nokia,” who told him that Nokia Maps would “effectively replace almost everything that Microsoft had developed over the past several years in terms of the Bing Maps infrastructure”. Sterling writes:

I said I couldn’t believe Microsoft would agree to swap in Navteq for the guts of its own system. Yet my lunch guest argued that Microsoft’s role would mostly center on the Bing Maps UI — ironically not unlike Yahoo’s relationship to Microsoft search results — everything else would be powered by Nokia.

And there was another very interesting remark. He asserted that Google’s unwillingness to agree to a co-mingling of Google Maps and Nokia Maps or substitution of Nokia Maps on the back end was one of the sticking points that prevented Nokia and Google from coming to terms.

Navteq is a GIS data provider, owned by Nokia. It counts plenty of big brands (including Microsoft) among its customers.

Based on the circumstances, we can only file this one under rumors at this point, but as Sterling points out, Microsoft and Nokia were indeed quite vague on the details about any Map integration resulting from the partnership.

At this point, it’s unclear what would become of much of the progress Bing Maps has made on its own, and its own integrations – Bing Maps apps, for example. We’ve reached out to the Bing Team for comment, and will follow-up with any additional details.

Update: Bing simply gave us the following canned response: “Bing Maps has utilized Nokia content for road data, geo-coding and routing services for several years, through Nokia’s Navteq vector data business, relying on the quality of its data for core location services. The Nokia/MS partnership will enable deeper collaboration and an improved experience for our customers in the future.”