I got a half-useful answer out of CFL at the second attempt:
"Depending on trains usually max 6 bikes.
You need an international ticket.
During summer are works on the line Luxemburg-Liege.
We don't have details yet, but there is probably partly running a bus.
Buses don't take bikes.
May double check train times a few weeks before your' travelling to make sure that you train is not replaced by a bus."
So at best, our group should have to split between two trains, two hours apart. Oh well, as long as we know. Otherwise, riding another 35 miles via Line 163 to Libramont to use SNCB is looking attractive to me.
