According to the source - http://aeronet.cz/news/analyza-wind...rmaci-o-uzivateli-jeho-prstech-ocich-a-hlasu/ - the data is still transmitted even with Cortana uninstalled. Attempting to block the transmissions results in constant error messages displayed to the user.
I saw something like this. It said that the error messages are just a facade, that it still sent all the data.