As far as I know it reads from the first UV channel. It’s also troublesome to swap between materials, and transparent materials just don’t work. But the importer does read multiple tracks so perhaps you could separete the animation in different objects cached together. Just untick the flatten tracks box in the importer. You could also give more info as to what does your Alembic stands for. A simulation, a static anim object, or a cloth sim?
Again, it’s just my opinion maybe there is a work around. Good luck!