As far as I know you do not lose heavy cover if you use it.
That means that if you are flanked by a second squad while behind green cover you can use it to have nondirectional light cover against the second squad while retaining directional green cover from the first one.
It provided light cover even in terrain with other modifiers (water, roads etch.)
You also do not receive any suppression.
It is not a great ability but it is neither useless
..., atleast i think yellow cover is 0.25 so correct me if im wrong)
yellow cover 0.5 received (and 0.5 suppression), not 0.25 for most weapon that is, the Centaur seems to have lot more better modifier against units in cover for some strange reason....