Just managed to get Facebook to recognise my OpenID with the help of this post.
Unfortunately the facebook system doesn’t seem to recognise the delegate url (at least in my case). I associated the OpenID http://tom.morr.is (which delegates to http://tmorris.pip.verisignlabs.com/) with facebook. However facebook list the Verisign url as associated to my account instead of http://tom.morr.is, which should happen.
This kinda makes delegation a bit pointless with facebook, at least with Verisign PIP.