There is no such information and GBuffer and it is very unlikely to appear there. Unlike pre-rendered graphics, reflections here are calculated from existing scene image, so there is no separate dedicated pass for it.
Same with refraction. It takes existing composited picture and distorts it according to your refractive material.
Your workaround would be to adjust settings of these features before compositing. Gladly you do not need to have a render farm at hand to iterate on that, unlike conventional CG.