well yeah collective, that's true, but you would think there'd be an option to get the IBL on join just as there is one for IAL.
I think in 5.9x there was a point where it did do this but I think it had some serious issues. Maybe it was 6.x? I forget, but I do remember it.
Anyways, that's all you have to do is type mode #channel +b and it will receive the IBL. No you don't have to be opped for this to work and it will not give an error. In fact, I had figured this out by packet monitoring mIRC when you double click the window
It doesn't document this in the help file.