I suppose with all the footage we have been seeing recently where AAA has been used against ground targets (ZPU-2, ZPU-4, ZU-23, S-60, etc), the 57mm might just be a useful cannon to have around. How capable would the shells be against thick brick walls or concrete structures? After that, would the 57mm rounds have enough "behind armour" effect to make them particularly feared by enemy snipers etc firing weapons from tall buildings?
Putting a ZSU-57-2 up against an MBT would be a waste of a valuable infantry support weapon (in my opinion at least). From the way AAA artillery has been used in recent conflicts (even 20mm Oerlikon-equipped Crusader cruiser tanks were used in support of Churchill heavy tanks and infantry according to Bryan Perrett's The Churchill tank book (a really interesting book I must say), I dare say that the ZSU-57-2 would do quite well in this role providing its thin armour and open-topped turret was taken into account.
The APCBC-T round will go through half a meter of concrete or so and has a small bursting charge. The larger fragments will be good enough to go through some internal walls.