RS485, RS422 are standards. Every device must meet the specifications independent of it's supply voltage.
If you want detailed information, then reading the datasheets is a good idea:
MAX3488:
* -7V to +12V Common-Mode Input Voltage Range
* Driver Output Voltage (A, B, Y, Z)..........................-7.5V to 12.5V (independent of Vcc)
* Receiver Input Voltage (A, B) ................................-7.5V to 12.5V (independent of Vcc)