On Windows Phone 8? I've been using Windows Phone since the launch of WP7 and I've never heard of a competitor's browser being allowed, nor of a decision to change this. Windows 8 possibly, but the OP seems to be confused between the two because Windows 8 doesn't run on anything ARM made by Nokia.
Ah, well, people seem to believe that my above post is a troll, so let me elaborate.
Windows 8 explicitly blocks the installation of any browser other than Internet Explorer (+ skins) on ARM. This is not due to a technical reason. This is due to the fact that Microsoft imitates Apple's policy that prevents any browser other than Safari (+ skins) on iOS [1]. While anti-trust rulings have forbidden Microsoft from doing this on PCs, Microsoft claims that ARM-based computers are not PCs and that the anti-trust rulings therefore do not apply. I therefore suspect that Microsoft will continue with this behavior unless a court of justice decides that ARM-based computers are also PCs. Hence my above comment.
And if anyone wonders why we need open platforms for mobile devices, that's a pretty good reason.
