QUOTE
VEHICLE WEAPONS AND RECOIL
Theoretically, vehicle weapons mounted in a weapon mount (p. 146) do not suffer negative recoil modifiers, but this can lead to strange results when a very large gun is mounted on a very small vehicle. For example it is possible to install a weapon mount with HMG on a compact drone with a body rating of 3 (human-sized) and suffering no recoil effects from full auto fi re, where a normal human would have trouble holding the weapon let alone successfully hitting anything. In instances like this, it is perfectly all right for the gamemaster to apply negative modifiers equal to those a person shooting the weapon would suffer from recoil, counting in the vehicle’s mass (as a rule of thumb: its Body rating) as recoil compensation.
Emphasis mine.
Technically, it says both. The easy way is to say that vehicle mounted weapons have their recoil compensated, but the more granular (I hesitate to say realistic) way would be, as mentioned at the end of the paragraph, to provide the vehicle's body in recoil compensation. What remains to be determined, then, is what "instances" the book speaks of. I prefer to assume that this rule of thumb just applies at all times because it means that some high powered weapons mounted on smaller vehicles can still suffer recoil modifications.