Pull up to 5V on a wire that may occasionally see 60V
To avoid current going "into" the 5V rail when there is 60V on the wire, put a diode between the 5V and the wire. (Anode on 5V, cathode on wire.) You may want to lift the 5V source to 5.4V or so to compensate for forward voltage loss of the diode at zero current. Also make sure you choose a diode with > 65V rating.

To avoid too much current going out of 5V when the wire is "at" -60V (whatever that means,) add a current limiting resistor. 1 kOhm might be enough; 10 kOhm should be plenty in most cases.

The design question you need to solve, and haven't answered, though, is: What is the source impedance of the +/- 60V? And how important are the 60V? If the 60V is "some other signaling protocol" then perhaps the source impedance there is high, and you need to make your 5V source current limiting resistor be high enough to not interfere with signaling.

Also, how important is the 5V? Is it for signaling, or will it power anything? What is the load impedance that will "see" that 5V?