Google Maps will soon work on Windows Phone because of "recent improvements to IE mobile"
Google said in a statement on the matter:
We tend to believe Google's reasoning, but the one trouble with it is the timing. Google's excuse is sound: IE mobile used to be pretty terrible and just couldn't handle Google Maps' HTML5. That's a perfectly reasonable excuse, because it is true. IE 9 on Windows Phone 7/7.5 did not have good HTML5 support and just couldn't do what Google Maps asked of it.
The trouble is that Windows Phone 8 and IE 10, which is far better with HTML5 support, has been out for a bit over 2 months now, and Google has only just decided to change the redirect policy for IE mobile. Google says that IE mobile "did not offer a good maps experience" in the last test, but doesn't mention whether that last test came after WP8 and IE 10 mobile came to market.
Ultimately, it seems that at the least, this wasn't a malicious blocking of a product. As with most things Google and Windows Phone related, it seems more like a matter of apathy or indifference. The Windows Phone market may be growing, but it isn't big enough for Google to put many resources towards it, and it took a public shaming for Google to take notice.
source: The Next Web