When the UPS is EPO'd, the battery breakers are tripped and the inverter is turned off. There is also an option in the UPS Tuner (Schneider software) to have the UPS go to static bypass on EPO (default setting is no).
The UIB (Unit Input Breaker) is not tripped. Tripping of the upstream breaker could be a code requirement, typically if UPS is located in the data center. This should be left up to the engineer of record for the installation.
Note; in parallel systems, only the UPS in which the EPO is activated is affected; remaining UPS will still be powered.