It seems that George Hots made it to software unlock Iphone 1.1.2 OTB 4.6 and chances are that this will work for 1.1.3 as well.
here his blog:
http://iphonejtag.blogspot.com/2008/02/11246unlock-good-enough-for-prize.html
I will personally wait a little, since the guy upgrade a baseband 3.9 to 4.6 and then found the exploit. I want to make sure that a pure native 4.6 works. As soon as the solution prove to be stable i’ll go through it and let yo know. But it seems that the dawn is close…
and as often iClarified make hard things easy with a fool-proof tutorial:
http://iclarified.com/entry/index.php?enid=649