Glad you got the Tivo to work with your mom's DTA. Those DTAs are manufactured by Thomson/Technicolor. They are pretty neat. One of my four DTAs is of that type, with the other three being the larger boxier model. Here is more specs on that model of DTA:
»184.108.40.206/index.php?id=3&Prod ··· dID=1161
»220.127.116.11/assets/images/Produ ··· pter.pdf
ADDED: I just read on a Comcast forum that the remote coding for the DCI105 DTA corresponds to a 51982 code. See if that is useful.