Very interesting. Perhaps the article should be titled "boy discovers conditions under which bacteria eat plastic". It still seems like introducing the new bacteria into the environment would be pointless, though. If the conditions in the landfill are left as they are now, I imagine the new bacteria would evolve back into what is presently optimal. If we modify the conditions, these new strains of bacteria would evolve on their own anyway... I guess I am assuming there are no local nash equilibria in the competition between different strains.

It's rather simple to modify the environment of the bacteria, normally plastic in landfills is surrounded by refuse of all different kinds, like paper, metal and the rest of the crap of modern civilization.

The key here would be to select out the plastics that these bacteria thrive on and seed the entire mound with these bacteria. I'm assuming the reaction will naturally be exothermic, which a sufficiently large bacterial density mixed with the naturally insulation properties of plastic should help the pile get near optimal temperature on its own.

However, there are obviously other factors. Do the bacteria release chemicals that are poisonous to themselves? Does the pile need good ventilation? Does it need sunlight or water? Petri dishes and shreds of plastic bags are a good start, but a lot of other factors need to be worked out before we're going to start breaking down enough plastic to matter.