The PAL version autoboots just fine, I've made a DL copy of my original and it works perfectly. The NTSC version doesn't autoboot though, as nutta_nic said, it has a built-in check and comes up with a "Please Insert Super Smash Bros Brawl Game Disc" message when you try.
I have a banner-bricked Wii and was hoping SmashStack would be the thing to fix it, but unfortunately it only works on NTSC copies of SSBB currently. If a PAL version is ever released, I'll finally be able to bring my Wii back to life!