Oh bloody hell.
Let's think like a criminal hacker for a moment.
If it were plainly that simple, it all boils down to if the iPhone connects to iCloud over any SSL connection.
If it does, that's a bigger issue that they can't work themselves really out of.
If it does not, all the FBI would have needed to do was use a packet sniffer (like Wireshark), sniff the packets at the WiFi router (hint: if not over SSL, VPN, or some other secure connection, data contained in the packets could be in plain text format), grab the password in question, and they would be done.
Now they've shot themselves in the foot here and are going to the well to get help for something that can't be done.
BL.