HD-TVI is emerging as one of the leading HD over Coax formats along side HDA/AHD. TVI alike AHD is not limited to a particular manufacturers offerings but it is also the most flexible when it comes to backwards compatibility with analogue. You can mix and match in any configuration, analogue and HD-TVI cameras up to the maximum channel amount. This makes it a perfect upgrade route if you want to upgrade/add to an existing analogue installation.
HD-TVI is also known as Turbo analogue within the Hikvision range and their recorders even allow you to add an IP camera or two from their range (networked separately)