Come on, it only makes sense, if we're going to have SSO at all.
Here's the response:
Ubuntu SSO is an openid identity provider (see for example askubuntu.com where you can use Launchpad as your identity). If Phabricator supports openid, you could use that to integrate easily.
It unfortunately doesn't support LDAP, and only supports OAuth 1.
Feel free to bzr branch lp:canonical-identity-provider and check out docs/resources/token.txt for info on how to get oauth tokens. This is, for example, the authentication mechanism old versions of Ubuntu Software Center used. Be warned that oauth support might go away in the future though.
You can also file a bug at https://bugs.launchpad.net/canonical-identity-provider/ to get it to the wider attention of SSO developers, because this address is mainly for login issues and as such, the visibility and help I can provide are limited.
I'll look more into this.
It is open source after all... You might be able to write a plugin for our instance and make it a Git submodule that you put on GitHub somewhere...
Would you be open to writing that code?