I'm not at liberty to discuss its identity, but it was an advanced military machine.
Perhaps they were necessitated by its requirement to operate at under e.g. 9g. Was it triple spool? Assume you can't mean RB199.
FWIW, I believe the GEnx (748, 787) has differential contrarotating bearings.
Perhaps this is because it is not always possible to design out the need for intershaft bearings on counter-rotating twin spool designs that require more stages & hence longer, less rigid shafts? Hence not only are intershaft bearings not a systematic drawback of triple spools as earlier implied, but they are infact potentially more likely on longer twin shaft designs?
I note the Trent has a frame/bearing box situated between the HPT and IPT. It seems to me that has the effect of negating the synergistic vortex exiting the HPT blades into the opposite-rotation IPT.
Perhaps someone can tell/show us what these radial struts (aerodynamic static structures) between the HPT & IPT look like....
Why would these stators be of particular interest, apart from industrial espionage if they are of novel design of course?
