If this is anything like the technology used in Sweden, it's a net positive -- it burns at such a high temperature that the emissions are essentially just carbon.
And let's face it -- plastic recycling has been a dismal failure, and we were all duped by the plastic producers into thinking that recycling was an environmental choice. Turn those petrochemicals back into combustible material, and generate some power while diverting huge amounts of waste from landfill.
FYI, Sweden's program was so successful that they started accepting trash from neighbouring countries to keep the incinerator running.