The MTS box is like 3 separate set-top boxes, in concept. However two of the conceptual boxes output only RF on those other two channels (8 and 11 in your case), and are controlled with RF remotes.
The Series 2 DT TiVo has support for only one box, on its A/V input, and only IR (on the primary unit address) or serial control (not compatible with the gateway). Its dual tuner feature is only supported when you have analog cable; which MTS simply does not provide.
That said, you could manually record one of the other RF channels from the gateway, using its RF remote to change channels. You will not get automatic recording from the TiVo at all. You can also use TiVos analog tuners it in a limited fashion with antenna.