Capstone Turbine Corporation makes the LNG burning turbine for this application. Here is a good video about it, showing the vehicle in operation and explaining the trade-offs; basically high initial capital costs with good long term savings in fuel and maintenance. Regenerative braking is a big win both in fuel savings and maintenance for garbage trucks which can perform more than 1000 hard stops per day.
Technical details on the turbine include; 200 lbs, 250 hp, 40,000h service life between overhauls (13+ years @ 8h / day.) The turbine has air bearings to eliminate wear, which implies a gas generator/power section arrangement to drive the generator, I believe.