If you want to use the TS5A2066 on the logic level data it should work fine.
You can not use it on the differential RS485 bus side because the diff pair can see very high voltages relative to the 5.5V rating of the TS5A2066.
TS5A2066 Analog Voltage Range, page 2 of the datasheet, allows for -0.5V to V+(VCC) +0.5V.
So with power VCC off to the TS5A you are only allowed to put 0.5V on the analog inputs.
This effectively makes the data lines 'not isolated' when power is off.
Perhaps you can provide more details to enable other suggestions.