There are many ways to do this. The ones below
1. Shared line appearance, where a receptionist will have the same lines as the executive.
2. IPMA; executive can decide to divert calls, take calls, or have the receptionist intercept calls, etc. The receptionist can also monitor the state of the line through a web interface.
3. Attendent Console; receptionist can monitor all lines for whomever is in ccm. The receptionist will not be able to intercept any calls from the console. One way around that part is to put the phones in a call pickup group. If the receptionist sees the phone ringing on the screen or hears, all she would have to do is select the pickup softkey.
My organization has been using the Attendant Console and the repectionist seem to think it is the easiest and most enjoyable for them. Also everything was done with the click of the mouse and drag and drop for answering calls, transfering, etc. The shared line appearances got to be more of a hassle. The IPMA did not work out because the executives did not want to have to learn how to use it and never knew if the receptionist would always be there.
There are probably more advanced ways of doing what you want too.
hope this helps,
John