Is it possible to send notifications to my Mountain Lion desktop when my iPhone receives a phone call?
Without a jailbreak what you ask is definitely not possible right now.
With a jailbreak there seems to be some apps that can send notifications like GrowlNotifier.
Connect can show notifications on your Mac when you get a phone call. It connects to your device over Bluetooth and will 'ring' on your Mac. You can also make/receive calls on your Mac. No jailbreak required — works over public APIs for Bluetooth.
With OS X Yosemite and iOS 8, you can use Continuity to be notified of incoming calls and answer them on the Mac.
I use Phone Amego to do that very thing on both OS X 10.7.5 and OS X 10.9.4. No jailbreak required. Works like a charm over bluetooth, and also allows logging/sending SMS.