I have and currently use directv deca boxes as pseudo "moca" devices to get the Internet and TiVo mini signals through my household coax, so yes it is possible. As mentioned here before, they run on different frequencies and that is why DirecTV had to make theirs proprietary. Cable moca signals run at different frequencies than DirecTV's deca does, but it's basically a Moca signal, just on a different frequency band.
Also as mentioned if you try to use deca on cable tv, they would interfere with each other and vice versa if you try to use moca with directv it will interfere.
The way around this is, run the cable RF or antenna RF directly to your TiVo, then using your directv deca boxes (again, pseudo moca), create a separate deca network (same as moca, just uses different freqs) throughout your home using the existing RG6 coax installed. Place one deca as the bridge near your router which will inject the Ethernet signal and modulate it onto your coax, then use other decas and their ethernet ports to demodulate back to ethernet for wherever you place a mini. You can also place an Ethernet switch between the deca and mini if you need wired Ethernet for other devices in that location.
Works like a champ here, good luck! Decas are way cheaper than moca adapters on Amazon and eBay too!
Director, Event Technology