Speaking as a game programmer, we wouldn't know anything about the "bus width", unless we were really pushing a system super hard. And then we'd only know it based on how we are being limited, we don't care about actual numbers (like on iPhone 4 where we know the system has a poor fill rate, but we don't know or care exactly what that fill rate is, we just know that we need to keep high-res textures to a minimum on that device). And I doubt Nintendo would include that sort of number in their documentation.
And as far as I'm aware, an SPU is a marketing term Sony/IBM came up with for the dedicated-task processor cores their cell chip has, so unless Wii-U is powered by a Cell there is no "number of SPU's"