With Lync I am able to subscribe to ConversationManager.ConversationAdded and detect Outbound Calls.
What I would like to do, is when a user dials a number, before that number is connected to the other party endpoint I would like to perform a check and depending on some business logic, either allow the call to go through as requested or redirect to a different target endpoint instead.
Going through the library documentation https://msdn.microsoft.com/en-us/library/office/jj937258.aspx I believe transfer would only transfer the local side.
I must do this on the server side and the rules will change from call to call, so i cant use a static routing/translation table.
Is this possible with Lync? Where would I look in the C#/dotnet API or do I need some other technology?
You could redirect using the SIP Application API which is documented at https://msdn.microsoft.com/en-us/library/office/hh364822(v=office.14).aspx.
For the purpose of rerouting an incoming call you probably should investigate MSPL specifically https://msdn.microsoft.com/en-us/library/office/hh364805(v=office.14).aspx