We do not have a cookie sync with Twitter at this time. Based on https://dev.twitter.com/ads/audiences/ta-realtime-integration-guide#idSync it looks like it may be possible. You have to have your Twitter-assigned partner id and the user’s id in the partner system, but I'm not sure what the response is since it's an image request. We are going to reach out to our Twitter contacts and see what we can find. Most clients use the email address at this time.
From our research, the Facebook ID sync is very involving (part of it being the customer has to approve of the website to get access to their FB info including the ID) and no client at this time has yet to attempt to do it outside a solution like Gigya. We (being me) are open to working with you on trying to do the sync outside of a tool like that so that it can be documented for future clients.
I've looped in our technical partner integrations manager to help with Twitter.