Right, typical marketing-driven idea.
Remember the ads for the (first incarnation of) iWon.com? A search engine with a great strategy--every search you made on it entered you, for free, into a sweepstakes with a $1,000,000 prize. (The original campaign featured an office worker whispering "If I win, does my boss get the money or do I get the money?" The announcer assures her that she will get the money). Surely a fantastic strategy. Surely every office worker will switch from Google to iWon.
The only problem was that iWon's search was mediocre, while Google's continued to be good. In the end, people use search to find things.
So, put aside the clever-clever strategizing. What will determine the outcome is how good the product is. Do their technology people have technology in Cortana and Bing that is meaningfully more helpful than Siri and Google? Not just a tie, not just a debatable slim edge.
If Microsoft can make Bing as much better than Google as Google was better than Altavista, then given competent marketing they will win.
If Bing isn't much better than Google, no amount of clever strategizing will help. Marketing could not save the Zune, or the Kin, or (way back when) Microsoft Bob, because the product itself was not compelling.
You can build all the Trojan Horses you want, but they won't do a thing unless they are just so cool that the Trojans can't resist bringing them inside the gates.