So please forgive me as I'm not as familiar with the configuration of standing up MS OCS or LYNC, but don't these operate in the same manner as many systems before, the client talks to the server inside your environment? Based on the multiple network segments you would have, it sounds like this would be a VERY difficult task to trace down one point where you can see all this traffic (further complicated if there is redundancy or load balancing) to process.
In most cases this would better be handled by the Agent as it could analyze the documents or sensitive content on the endpoint device. The other question would be, what is the use case to monitor files internally? If it's to stop cross-departmental communciation of sensitive content, then again this is a better case where you would want the Agent to help solve that issue because it can handle both this as well as other internal use cases that Network coverage may not.
The root cause for the Network coverage, would be to really cover anything sensitive leaving. Many times we work with customers to really understand what the problem they're tryign to solve is, because it may be something that was brought up, but not actually critical to protect (insider to inider information for example).
Lastly, based on the fact that you are on V10, I would say the likelihood of the network engine to understand that protocol may be a bit degraded as both OCS and LYNC are newer MS products using newer protocols.