Yes, you can bind to the follow event, and if a follow occurs somewhere in the flow of the popup web intent, we will pass back this event. If you are using the Follow Button, then the event.target will reference the iframe which generated the follow (even if the follow occurred in an intent popup window). If you are using normal anchors + web intents, then event.target will reference the anchor tag that originally spawned the intent popup.
twttr.events.bind('follow', function(event) {
console.log('The follow originated from', event.target);
});
Let me know if this answers you question.