nad, I had a short look at the article. (Actually I should run to meet my real worms before it gets dark.) It's just a meta study, and I strongly suspect it is worthless: Soil can not be studied alone, there's always interaction between aboveground and belowground life. E.g. worms drag plant litter into their burrows, let it rot a little, then munch the goo (plus lots of dirt), and the resulting worm droppings gives excellent new soil. As long as soil accumulates that way or is at least balanced, I don't see how worms contribute to CO2 emissions.
BTW, I'm experimenting with char coal worm compost. The worm population that stabilized over the last 2-3 years seems quite different to what you would meet in usual compost, with lots of enchytraeids at the younger char coal. They seem to be an amplifying feedback on acidity. Folks call me crazy, but they are fascinating animals. E.g. one sort enchytraeid lives on glaciers: [Ice worms](http://en.wikipedia.org/wiki/Mesenchytraeus) die (dissolve) when it gets warmer than 5°C.