I'm not sure why you want to add ABS but it is possible if you know how to wire things properly.
And yes, ABS did come on 8.25s in the Liberty, Durango, Dakota (iirc), and several other C/J/D vehicles. But as someone noted it is a single tone wheel at the ring gear, at least on Durangos it's machined into the lip of the ring gear carrier flange. I am unsure about tooth count but it is most likely 108 teeth instead of the 54 I'm fairly certain XJs use, so you can't just splice both rear wheel sensor signals from the ABS HCU into it, you're going to need at the very least a PLL circuit and probably a lot more than that (possibly including DDS chips and a microcontroller, DSP, or FPGA) to convert the signal in any way I'd expect to work, depending on how smart the ABS HCU is.
Also, the XJ 8.25 center casting has the bosses for the ABS pickup, but they aren't machined out, so you're going to need to measure angles/positions relative to some sort of datum point (probably the centerline of the carrier bearings), find a machine shop that will work on a rusty ass 5 foot long oddly shaped bit of metal, and have them machine a few faces flat, bore a hole, and drill/tap a few mounting bolt holes in the center casting. It's probably not worth doing. As I recall people have put ABS on 8.25s but it focused on swapping ABS backing plates from a d35 out of an ABS vehicle and having the shaft shoulders and tone rings custom machined to fit properly. I'm not entirely sure on that, I may be thinking of the XJ D44 ABS swap someone (Talyn?) did.
Basically: you are in for a lot of pain if you try and do this. Either custom machining or custom electronics or both.