This is one of those things where the whole is greater than the sum of its parts. Milk (or cream) and lemon juice don't play well together. However, eggs and lemons get along fine. The key is to add the lemon juice at the approraite time. This applies not only to ice cream, but also to certain butter creams and pastry fillings.
Here are links to two recipes from different sources. But both confirm what my recollection was .... you need to add the lemon juice it a particular point in the process .... when the milk or cream is, in effect, "immunized" by eggs against curdling.
http://www.roadfood.com/Forums/topic.asp?TOPIC_ID=1600http://www.razzledazzlerecipes.com/icecream/crelemon.htmHope this helps.