despite the wallet app technically being able to do it.... as far as I know, it's not working yet (in the US on AT&T at least, not sure about everywhere else)
ISIS has confirmed many times that they have something planned for WP8 "soon". The Icon, when initially marketed, claimed to support ISIS mobile payments. So the possibility is there. Now that Cyan (and 8.1) will slowly be popping up on devices, hopefully the soon part from ISIS means over the next couple of months