I think that cats are lactose intolerant, however some cats can tolerate a greater amount of things than others.

Using dogs as an example with pancreatitis...

One dog may eat greasy hamburgers, pizza, gravy and such on a somewhat regular basis and not get sick while others may get deathly ill from just one treat of the same foods.

I think with both it's the system of the individual animal that makes the difference.

As a general rule I wouldn't give any dairy products to cats, particularly high fat ones, but I suppose a tiny amount on a rare occasion as a treat shouldn't cause a huge problem I wouldn't think.