Xfinity can't take over an ADT system with wireless sensors?

Hi, I had a tech visit this morning to add Xfinity home security. When I initially asked if they could take over existing systems with wireless sensors, I was assured by Customer Support that they could and "typically had great success with DSC panels" like the one I currently have. I have about 20 window/door sensor and 5 motion detectors, so replacing all of them would be prohibitively expensive despite the savings from bundling the service with internet/tv. 

When the tech arrived, he looked at 1 wireless window sensor (a honeywell 5816 that currently connects to a DSC panel) and said xfinity can't use any of the existing sensors (door/window, motion, smoke, etc). I didn't feel like he tried very hard and was out the door in under 5 minutes. It was a waste of everyones time. 

Is it true that no existing DSC or Honeywell equipment can be used? ADT used a receiver converter to connect the old honeywell equipment when they added the DSC panel. Are there no receivers can that translate existing sensors so xfinity can use them? 

It just seems so logical that xfinity would have a way to do this so they could win business from people with existing systems. But maybe not?