Nav, Comms, and radar are all essential AC powered devices. These loads would not be shed during SE OPS. The operating engine generator automatically powers the failed engine's AC bus and a manual bus tie can be initiated if needed.
The only common scenario where the above mentioned avionics would be lost is if there was an AC bus failure, or electrical control box failure, however, it would only be half as the remaining side (NAV1 or NAV2, etc) would remain powered.
As essential electrical equipment*, communication radios, navigation gear, and radar would be unpowered in the case of the loss of GEN1, GEN2 and the APU generator or a bus failure as mentioned above. Even in such an emergency electrical configuration, there typically remains at least one COM, one NAV unit, etc operational. This arrangement is fairly standard across all large transport category aircraft.
*with the exception of the HF radios and SATCOM, if fitted.