I don't know for sure but probably a very long way. Cat 5 data cable starts attenuating pretty bad past ~320' and that's required to carry a data signal. All you're doing is switching something on or off.
The PIR uses 5VDC and the input board it is triggering is active high. I should be able to get within 60 feet of sensor with the input board so I believe it should work fine. Was wondering what the limit was for a system like this.
You'll be just fine at 60 feet. You might want to use Cat 5 just because it'll probably be cheaper than spool wire and it already has several conductors in it. Cat 5 is used frequently to build incandescent light SSRs well over 100 feet away from the light controller, and the SSRs are just optocouplers running on 5v.