Here we are again with a common customers request.
How to customize the meeting invitation?
Well, the answer is: there is no supported way. As it is hard coded and has no template.
But, You can add a custom message to a meeting request by defining a transport rule on your Exchange Server 2010 or Exchange 2007 Hub Transport Server.
Every Lync 2010 meeting request contains a hidden text identifier, [!OC()!].
In the Exchange Management Console on the Hub Transport Server, define a transport rule that searches for this identifier by using the option when the Subject field or the body of the message contains specific words. Then enter the custom text you want to be displayed.