I don't know about it for Listeroids particularly, but it's a very common tweak for diesels used in stationary applications where natural gas is available, like natural gas pumping stations and so on. The governor systems I've heard about (on engines in the 200-2000 HP range) injected a constant baseline of diesel fuel and governed to match load load with natural gas injection.
combustion-wise any hydrocarbon gas is roughly equivalent to any other - the only difference is energy content/unit volume (which is dependent both on chemistry and temperature). The big gotcha with stuff like producer gas is the semi-combustible crud that plates out when it hits a piece of cool (even 190F) metal. Intake valves sticking closed on shutdown is not unheard-of. Ash uptake might also be a concern with wood gas as well, and filtering hot wood gas is probably not the easiest thing in the world. Corrosive components can be a concern as well.
