Actually Cortana came on all windows phones running 8.1. We had their 50 buck entry level phones with full Cortana.
I really miss that Cortana would read my incoming texts, and give me the option to ignore, call, or text back all through my bluetooth. It was a very handy feature for me to have my phone do everything by voice, because I'm on the move alot, and fighting a phone in and out of your pocket all day long gets old. Plus much more chance of dropping or losing your phone (I've done both)
If there's a way to get my android to read incoming texts and announce callers I would be a VERY happy camper lol