well, here is what i think the step by step test process should be...
1. see if the hub/stud plates can be separated from the bearing assembly. If they can...
2. can the sti or tribecca stud/hub plate be installed/pressed in to the legacy bearing/knuckle flange assembly. If they can...
3. test fit hybrid asembly on legacy along with 5x114.3 rear rotor and brembo rear caliper with pads. if everything fits( the rotor fits properly on center with the caliper) then more on to worrying about axle splines. if not, a special caliper bracket may have to be made to get the caliper to fit over the rotor on center. this may affect wheel fitment, but doubt it since its the rear.
4. since the female axle splined part is on the transferred 5x114.3 hub/stud plate, the lgt alxe has to fit in to that spline pattern. if it does, we're set. if not, for R160 people, will a tribecca rear axle work? or, maybe the outer axle stub with the right spline pattern can be installed on a LGT rear axle. for r180 spec b people, maybe the whole sti rear axle would fit.
if you get all 4, we got ourselves a fairly cheap and viable hub conversion for the rear.