First you need to recompile wireless-tools package as PowerPC64. Currently there is a bug in kernel (or feature) that does not allow ioctl32 calls to be used correctly. Therefore this causes ydl's default wireless-tools package not to work as it is compiled as PowerPC32.
To recompile it you need source RPM for wireless tools package: wireless-tools-28-1.src.rpm. Install it. It should extract some files under /usr/src/yellowdog/*/*. Unfortunely this package has problems compiling for ppc64 so this needs to be fixed first. I have made a patch for it which can be found from yellowdog-devel mailing list. Basicly you need to copy that new makefile patch file over older makefile patch file and then you can build it. After that just run "rpmbuild -bb wireless-tools.spec --target=ppc64" and it builds could of RPMs to /usr/src/yellowdog/RPMS/ppc64/. Install wireless-tools-28-1.ppc64.rpm package (rpm -ivh <pkg>). After that you can use iwconfig, iwpriv tools nicely and configure WPA.
To get it working automatically you must modify two files:
(others can be left empty)
If you don't use DHCP for some reason configure rest how you like.
Change "set_alg 2" to "set_alg 3" if you have WPA2-PSK (AES). I didn't get WPA2 working and I think it is hypervisor's firmware issue (as it works correcly in GameOS). This might be relative you Wireless Accesspoint in use or your PS3 hardware & firmware version. Check how it works, and tell us if you have success.
Oh. YDL's wireless kernel driver is a bit old, so AP scan might not work correctly. It is possible to compile newer driver for YDL but I won't go to details this time.