A partial explanation of what the liver gets up to (because, no doubt, it is far more complicated) is that it can release glucose into the blood stream when it detects the BG levels are low (also known as the dawn phenomenon, but no doubt it can happen at any time).
When alcohol is in the blood stream, the liver is 'too busy' to release this glucose and so that is why there is a greater risk of hypos.
This also explains why it is possible to get a hypo when on metformin, because metformin also restricts the ability of the liver to release glucose into the blood stream.
Oh, and another thing, I don't think that the liver is particularly responsive to low BG levels. It can happen that it will still release the glucose even when you've just eaten and the BG levels are already on the way up, then causing a hyper!
Andy