No, the reflection of object to background is not so important, it is important i have a trancparenty background, and an Object with a reflection Material as chrome or aluminium, here another example for understanding:
i have a sphere, and i gave him an aluminium material, than i adjust in Vray option enviromoment to make Background White. Then i render it, after that i switch to alpha cahnnel in the Frame buffer an save this as png-file. In the moment to switch to a alpha channel the Backgroung change to Black and the Sphere Object take white (without aluminium material). When i open the File, i see the same picure before, background black the sphere white (without aluminium material.).
when it helps, i would attend a picture example in the tread
knot