Unity Connection works fine with both Exchange 2007 and 2010; it uses EWS in both cases to interact with the mailboxes. The good news is that there is no more MAPI dependancies. This also means that the Single Inbox feature is not identicle to Unified Messaging from traditional Unity. The Telecom team needs to read the product documentation, esspecially the Unified Messaging Guide. Along the same lines they should also spend some time understanding the new ViewMail for Outlook (if you use it). The clients are not interchangeable!
My main suggestion is to ensure that you have Exchange AutoDiscover working from day one. When they install Unity Connection and configure the UM Service account they can choose whether to manually specify a CAS server or use AutoDiscover. If they use the later you have to coordinate your actions far less going forward; CXN will figure out where the mailbox is usign the same methods Outlook does.
Lastly, when it comes to upgrading from 2007 to 2010 it's not a major effort. Just re-read the integration guide and make sure that the 2010-specific tasks are done. If memory serves there is a new application-impersonation role or something in 2010.
Please remember to rate helpful responses and identify helpful or correct answers.