I might be wrong here, but I'm not sure that it's going to work out that Google is the "competition". Google seems to favor a strategy of getting their software on as many devices as possible, and siding with one mobile company and in some way freezing out or disadvantaging the others seems counter to the entire approach they've taken.
My understanding of it, at least from reading the BBC and Bloomberg, is that the main motivator behind the purchase wasn't to get a mobile company. The real motivation is that by buying Motorola Mobility, they don't get only the company - they get its patents, as well. As you are no doubt aware, there is a huge patent war in mobile technology, with companies suing each other over what is proprietary. Google and Apple sued each other recently, and now HTC and Apple are suing each other. By acquiring Motorola mobility, Google bought about 17,000 patents on various aspects of mobile technology.
I don't think this is about changing the way Google operates - I think it's taking strategic territory in the patent war.