Thanks for pointing this out. I understand that EDF was the driving force behind this initiative, but the fact that the sensors were mounted on Google cars seems to have diverted attention from that fact.

There's a growing effort to monitor CO2, CH4, and CO at very fine spatial scales, and to do inverse modeling to infer emission rates ("fluxes") from the snapshots. (E.g., https://megacities.jpl.nasa.gov/portal/)