So far my research has turned up that they indeed bolt right up, splines are identical, 99-01 WJ airbags perfectly match XJ specs and will work the same as an XJ airbag, I believe the same 99-01 WJ cruise controls will work, but I haven't found anyone that has made the radio controls work. I found a single thread on the Jeepin.com forum board where they talked hypotheticals and discussed whether or not using a 99-01 WJ clock spring would work. Also unsure if the BCM would need to be used to accept the inputs from the radio control switches or if for an aftermarket radio, using an aftermarket radio to OEM steering wheel control adapter module can simply be tapped onto the exiting pigtails off the clock spring.
So those are my unanswered questions and I don't know enough about all those circuits to test it all out. But if someone knew the answers then I will be the Guinea pig to try it all out.