There is a substantial difference between a 57mm cannon on an IFV using airburst shells a dedicated radar-directed anti-aircraft gun system using the same sort of ammunition. The former may be able to lase and engage a helicopter at moderate ranges with such ammo but it’s going to have no chance of shooting down an incoming PGM like the radar-guided system could potentially do

I am not sure to what extent IFVs will be capable for AD, but they are supposed to be linked in the same battle management system in order to share targeting data. It is not the same to have only AD units taking care of an attack than having all IFVs contributing and raising your saturation threshold manifold. BTW the ZAK-57 AD system based on the 57 mm cannon uses EO detection and guides the ammo with laser (beam riding), not radar from what I know.

Good info about the system here:
http://nevskii-bastion.ru/zak-57-derivation-pvo/