Communication between Xi boxes and XG DVR

The way I understand it, Comcast is slowly migrating all customers to the Xfi cable system/equipment. And the Xi series boxes just borrow 1 tuner from the main XG DVR box when they are in use, correct? The same way a Tivo Mini borrows a tuner from the main Tivo DVR, supplying the video feed over MoCa. I am adjusting some coax wiring/splitters and want to make sure each one is getting a good signal. I opened a diagnostics menu on an Xi box, and under "MoCa", it says "Disabled". So how is it communicating with the main Xi box then? And how can I check performance? Thanks