This HAS been answered. Everything will transfer normally. The transferring process won't recognize the Homebrew Channel and so that will stay on the original vWii. As far as we know (I think) the Wii U on the receiving end won't have any evidence that the original Wii had homebrew on it.
I didn't ask what happens if the Wii has HBC (I know that this has been answered). What I was wondering is what happens if I install HBC on the vWii (on the Wii U side) and then run the transfer tool. I know (from another thread) that if I have saves from the same game on both consoles, the Wii ones will overwrite the vWii ones.