Must lactose-free milk be ultra-pasteurized?
You can now buy (at least in Switzerland where I live) lactose-free milk which is not ultra high-temperature pasteurized. They are kept chilled in the supermarket alongside "normal" milk. So I would say based on this, no lactose free milk does not have to be ultra pasteurized. Though I will note, they hardly tasted sweet at all and they are quite expensive, nearly double the price of ordinary milk.