Using RS485 over CAT5e Foiled Twisted Pair (FTP)
For RS485, CAT5 should be just as good as any other shielded twisted pair cable. The impedance should be within tolerance for RS485. What matters most is how you connect the common ground between devices, and how you connect the cable shield, and where you connect the terminators, but that does not depend on if the cable is CAT5 or something else.
The RS485 is defined by TIA/EIA so it means the same TIA RS485 standard.