Hey Conor
I am a user of CTI so perhaps I can help
OK.. theres two seperate phases to this computer control stuff with DCC. The first is providing the DCC signals and power to the track to run trains. That is accomplished by using a DCC command station, whether Lenz, Digitrax or any other system.
The second is computer control of many functions, such as switch control, signalling, timetabling, etc etc which is performed by a system such as CTI.
Now, most DCC systems can be linked to a computer, using that manufacturers computer interface, and if that is happening, then the automation system in use can, generally, be used to provide computer input signals to the DCC system, and hence control the trains using the existing Command station.
CTI is not a DCC command station and system, but it will work with existing DCC command stations to form a complete integrated system.
My personal system is a Lenz 100, LI101F computer Interface, and CTI with about 6 modules.
Now, with my system, since the Lenz system is linked to the computer as well as the CTI, this allows me to use the Throttles built into CTI to drive trains both manually, and automatically, but I still need the Lenz 100 command station to provide the actual track signals to do that.
With regards to wiring etc, I am afraid your going to need both the DCC wiring as normal, and probably additional wiring and sensors to make the CTI system work, but it is worth it, or at least, it is for me.
My CTI system provides a track plan on my computer screen of my layout, with all switches and signals shown. I have current detection circuits throughout the layout and based on train position, the CTI system controls all the signalling, grade crossing flashers, layout lighting etc etc all automatically based on train position. It also allows my to use buttons on my on-screen panel to switch switches and do route setting. It also has the ability to run trains automatically if I have had a hard day and just want to kick back and watch trains go by
Hope this helps in answering your question.
Regards
Graham