I just wanted to share something with the community as it is something I have seen a number of posts on and somethign we struggled with as a company before stumbling on this ingenious solution. I can't take credit for this, we found it online (Also sorry if this is a repost)
There is a simple, if somewhat kludgy way to do this. Any time we have a customer who needs to page both to an overhead and the phone simultaneously what we do is purchase a very basic model IP phone such as a 7912.
You then open that phone up and attach a single pair from a Cat5 cable to the leads for the phones speakerphone. Drill a small hole for your cable to come out of the phone and attach the other end of the pair to your overhead paging system. In this way, users need only dial the DN for the IP to IP phone paging and it will broadcast over both the phones and the overhead simultaneously without any sort of complicated additional configuration.
This is handy as a number of people I see on these forums aren't terribly familiar with the command line and this method requires no configuration that can not be done with CCA.
I hope this helps you guys, I know it's certainly been a great time saver for us when installing CME and UC500 systems!