nice, but the real problem with plastic bags is their existance in the general environment, especially in the ocean, where it's killing wildlife ... like with all recycling, the problem isn't dealing with the refuse, it's getting folks to collect it instead of flinging it over thier shoulder .... plastic film can already be recycled into other products, maybe without producing additional CO2, which is the catch22 in composting
bacteria have been used for quite some time to remediate contamination, and there are microbes that will break down nearly anything, providing the contaminants can be 'corraled' and the right bacteria added
Most plastics cannot be broken down, spilled oil can but the polymers that make up plastics are largely new to existence and as a result no bacteria exist that can break them down. in this case I highly suspect one of those new bags that is designed to degrade on its own was put into the soil/whatever and the bag broke down into little tiny bits of plastic rather than one big sheet of it. As far as I know no chemical tests were performed to search for the plastic. This is just another case of bad science reporting because most of the news outlets have sacked their science reporters.
There was a story about nylon eating bacteria back in the 80's but the truth of the matter is that the bacteria were not eating the nylon but rather a small byproduct of nylong production, bacteria can adapt to small molecules much more readily than large ones, its easier for an enzyme to randomly get around a small molecule than to work its way into the tight matrix of a polymer.
