As described in ubuntu bug report, it is impossible to store contacts
for SIP accounts:

https://bugs.launchpad.net/ubuntu/+source/empathy/+bug/294991

Instead ROSTER supports should be done at rakia level.

Thanks,

severity 736226 wishlist
tags 736226 + upstream
thanks
accordingly.

With upstream hat on: I'm not sure whether the correct answer is:

1) for Rakia to gain support for local contacts (which cannot be synced
   to other systems and will be lost if the account is deleted), or
2) for Rakia to gain support for SIP extensions like SIMPLE which will
   work on certain servers (?), or
3) for Empathy (which already uses Folks, the same library as
   gnome-contacts) to gain support for adding contacts to
   evolution-data-server via Folks if there's no "roster" support
   in the connection manager

Someone needs to decide which way is best, and implement it... my guess
would be "both (2) and (3)" but I don't understand the finer points of
SIP, so maybe (1) or (3) would be more feasible.

    S