FYI, someone needs to try test fitting this, but I do believe that the 08 WRX Sedan exhaust system is ALMOST same as the Legacy GT exhaust system (including the mufflers!).
It looks like the mufflers mount exactly the same, however the Catback flange looks like it is rotated at a different angle... However, a FULL exhaust may bolt on without any problem, as would a dual muffler kit like the Prodrive mufflers (just axle backs and not the catback)
The 2.5i's (non-turbos) look EXACTLY the same though...
BTW, i'm going by diagrams here not the actual cars, so it will need to be verified first.