In our office we also have the Cisco SIP phones, but they are about $1,000. So I don't they are so popular.
Regarding adding another phone, adding the device template is trivial--that takes 1 minute. All you do is specify a range of mac addresses for the IAXy and a configure script (like configure_IAXy.sh). Then when the dhcp server detects a new request from a device within that range, it automatically adds an instance of the IAXy device, and calls the configure script, passing in the IP Address, Mac Address, and device ID as parameters. So all that is trivial.
The work is in the configure script itself, since that's what has to do whatever needs to be done to make the device work. configure_snom.pl won't help too much since it's specific to the Snom. The Snom's have a built in web browser used to do the configuring. So what configure_snom.pl does is use wget and other internet tools to programatatically fill in the Snom's web page with the device ID, the server, etc., and then programmatically hit 'update' (a form submit). So the configure script has nothing really to do with Pluto--it's purely for setting up the phone.
That process is likely to be completely different on the IAXy device, so I'm not sure anything in the configure_snom.pl can be shared.