We researched this a while ago, as we were designing the interaction in Topics and their role in helping teams transfer know-how and we wrote a blog post about Why Some Teams Succeed (While So Many Fail Miserably)
There is an MIT study that found that success or failure of a team can be predicted by simply studying the group members' communication patterns. The researchers attached electronic badges to members of very diverse teams to collect data on whom they interact with, for how long, when and where. As it turns out, highly successful teams have very similar communication patterns. Their members communicate very often within and outside the organization and technology plays a key role in enhancing this process.
We too believe that communicating with the new hire in the way that the team normally communicates (in Topics, for instance) would introduce the new employee much faster to the culture of the organization. It is of utmost importance in the onboarding process that this new employee is exposed to the ongoing projects and considered, from the very beginning, an asset to the group.