If you are asking about marrying a Lionel switch controller with a MTH switch controller, then I'm very confident though I admit I don't have this configuration myself. The concept of two (or more) devices controlling a given switch is well established. That is, you might already have the manual lever switch controller connected at the same time as your command switch controller box (e.g., SC-2). For each switch, run 3-wires between the MTH and Lionel switch controller boxes as illustrated below. MTH labels the switch controller terminals 1,2, IN instead of #1,#2, #3.
If you're asking about what JGL suggests about a widget that would intercept DCS handheld-remote switch commands and convert them to a format that a Lionel switch controller would understand, then I am confident it could work...but I'd be amazed if someone has done so or has even pondered doing so.