Since the book refers to "12 satellites in orbit around Mars" (which we don't currently have), and they use the satellites to image each and every landing site to ensure the automated systems are going well before the astronauts land, I would suggest that the imaging technology isn't based on what is currently orbiting Mars but rather an extrapolation of what could be used in the future.
Putting an imaging satellite of such capability in orbit around Mars would be no more difficult than any other satellite around Mars - the imaging tech isn't particularly onerous, as Mars has a less dense atmosphere than Earth it wouldn't have the same requirements as imaging the same resolution would here, as well as the orbits being lower due to the size difference between Mars and Earth.
Edit: I'm in the middle of rereading the book at the moment anyway, and have come across a few additional bits of information and a discrepancy as well.
The additional information is that at least one of the satellites used is called "SuperSurveyor7", a satellite we currently do not have, which indicates that the satellites in place are not of current technology.
The discrepancy is that early on in the book the fact that they could fairly easily identify various things at the Ares 3 landing sight from satellite photos, including the fact that the MDV had been dismantled, the emergency pop tents had been erected and lined up, the solar panels were clean and there was no body on show.
However, later on in the book, they struggle to get anything more than a blurry shot even after the NSA has enhanced the image.
Now that could indicate that not all satellites are equal, but the batch of shots is part of 17 taken during a 10 minute period, which indicates more than one satellite involved. This is the only time they seem to have issue with satellite imagery.