When chilling a glass, you dump out the LN. OK. That makes some sense. But then when making ice cream, you put LN directly into the bowl while mixing. Huh?
edit: I can see why you don't want to provide too many details. I will just say this story, while very interesting, terrified me.
As long as your food or drink are not spewing off large amounts of gaseous nitrogen, there should be no liquid nitrogen in them.
It's also easier in many ways for them. You don't even have to have freezers, since you're spot freezing everything. It saves you from buying a batch freezer for making it, which is $30,000 used. I'm told that if you're buying LN regularly, the distributor will hook you up with the tank at a low monthly fee. So it's probably much cheaper to start a stand that way.
The downside is it's a little less time-efficient. It's REALLY easy to make a 5 gallon batch of ice cream in a Carpigiani.