How do you detect when the Network RPC buffer playback is complete?

When a new client connects to my server, I need to wait until they have 'caught up' on the buffered RPC calls before I make the client active. How do I detect whether or not the playback is complete / how do I determine if the client has received all RPC calls that occurred in the past, or if there are more to come?

Edit: I've been able to work around this issue by using Network.isMessageQueueRunning http://docs.unity3d.com/Documentation/ScriptReference/Network-isMessageQueueRunning.html to explicitly control when RPCs can be processed, but my original question is still relevant to me.