MY08 Wrx's etc have a stretch fit a/c belt...there is no tensioner needed as the belt is kind of like an elastic band.
This type of belt will be appearing on many more makes in MY10 vehicles.
Yes they still have the tensioner mounts. If you fit underdrive pulleys you use the my07 or earlier tensioner assembly.
Like the image below: 08 WRX engine, 08 wrx underdrive crank pulley, 08 Liberty A/C belt & 07 Wrx tensioner.......
