CaI2-I + PbIVO2 + 2 H2SO4 PbIISO4 + CaSO4 + I20 + 2 H2O

This is an oxidation-reduction (redox) reaction:

PbIV + 2 e- PbII (reduction)

2 I-I - 2 e- 2 I0 (oxidation)

Change the oxidation states